Revox A77 Service Instructions

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Service Manual

REVOX A77

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1. CONTENTS

2.	GENE	RAL Front Bond Boor Bond	Page 4
	2. 1.		0
3.	DISM	ANTLING	6
	3.1.	Removal of Housing	6
	3.2.	Removal of Cover Panel	6
	3.3.	Removal of Front Panel	6
	3.4.	Removal of Power Switch	7
	3.5.	Removal of Real Motors	7
	37	Removal of Canstan Motor	. 8
	38	Removal of Control Board	8
	3.9.	Removal of Power Transformer	9
	3.1 0.	Removal of Amplifier Cards	9
	3.11.	Removal of Potentiometer	10
	3.12.	Removal of Switch Board	10
	3.13.	Removal of Frame (Removal of Rotary Switches)	11
4.	MECH	IANICS	12
	4.1.	Headblock	12
		4.1.1. Tape Guides	12
		4.1.2. Head Mounting	12
	4.2.	Tape Tension	13
	4.3.	Brakes (Stop)	13
		4.3.1. Brake Torque Measurement	13
		4.3.2. Brake Adjustment	14
	4.4.	Pressure Roller	14
		4.4.1. Pressure Solenoid Readiustment	14
		443 Exchange of Pressure Roller	14
		4.4.4. Pressure Lever Readiustment	14
	4.5.	Capstan Motor	15
		4.5.1. Removal of Capstan Axis, Ball Bearings	15
	4.6.	Exchange of Reel Motor Bearings	16
	4.7.	Lubrication	16
	4.8.	End-of-Tape Switch	16
5.	ELEC		18 18
	52		19
	5.3.	Record Amplifier	19
	5.4.	Oscillator	20
	5.5.	Record Relay	20
	5.6.	Playback Amplifier	20
	5.7.	Power Amplifier (Loudspeaker Amplifier)	21
	5.8.	Power Supply	21
	5.9.	Drive Control	22
		5.9.1. Photoelectric End-of-Tape Switch	23
	5.10.	Speed Regulation, Capstan Motor	23
6	ELEC	TRICAL ADJUSTMENTS AND MEASUREMENTS	26
	6.1.	Demagnetizing	26
	6.2.	Tape Speed	26
		6.2.1. Pick-up Head - Adjustment	26
		6.2.2. Tacho Adjustment	26
		6.2.3. Tacho Adjustment with Cathode-Ray Oscilloscope	26

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	6.3.	Playback Adjustment 6.3.1. Azimuth Adjustm 6.3.2. Azimuth Adjustm 6.3.3. Playback Level fr	nent, Playback Head, Coarsé (Max Level ) nent, Playback Head, Fine (Phase Methoo om Test Tape	4)	26 27 27 27
	6.4.	6.3.4. Frequency Chara Oscillator and RF-Adjust 6.4.1. RF-Voltages and 6.4.2. Dummy Load 6.4.3. RF-Traps, Record	icteristic, Playback ( from Test Tape ) ment Frequency Checking d		27 28 28 28 28 28
	6.5.	6.4.4. RF-Traps, Playba Record - Adjustments 6.5.1. Azimuth Adjustm 6.5.2. RF-Bias 6.5.3. Azimuth Adjustm 6.5.4. Record Level 6.5.5. Record Equalization 6.5.6. Record Equalization	nent, Record Head, Coarse ment, Record Head, Fine tion		29 29 29 29 30 30 30
	6.6. 6.7.	Distortion Factor Measu 6.6.1. Distortion Factor 6.6.2. Noise Voltage (a 6.6.3. Noise Voltage, E 6.6.4. Erase Attenuation 6.6.5. Crosstalk, Mono 6.6.6. Crosstalk, Stereo Output Voltage Check	rement ^- (via Tape ), VU-Meter Calibration nd External Voltage ) via Tape «ternal Voltage ′′ Before Tape'' (Check) n		30 30 31 31 32 32 32 32 33
	6.8.	Wow and Flutter			33
7.	ACCES 7.1.	SORIES Remote Control			34 34
	7.2.	Timing Switch Operation	1		34
8.	MODII	FICATIONS Bowind			35
	8.2.	Switch Noise			35
	8.3.	RFI			35
	8.4.	Transfer Play Sensitivity			35
	8.5.	Replacement of Capstan	Motor		35
	8.6.	Capstan Motor with Slee 8.6.1. Removal of Caps	ve Bearings tan Shaft and low-friction Thrust Washer		35 35
9.	TROU	BLE SHOOTING			36
	9.1.	Faults in the Drive			36
	9.2.	Faults in the Circuitry			39
10.	DIAGF	AMS		Diag.	1
		Tape Drive VU-Meter Board Switch Board Input Amplifier Record Amplifier Oscillator Record Relay Playback Amplifier Loudspeaker Amplifier Speed Control	1.077.100 1.077.480 1.077.435 1.077.700 1.077.705 1.077.712 1.077.715 1.077.720 1.077.850 1.077.725	Diag. Diag. Diag. Diag. Diag. Diag. Diag. Diag. Diag.	2 3 4 5 6a 7 8 9 10

11. REPLACEMENT PARTS LIST

12. SPECIAL VERSION

12.1. Revox A77 – DOLBY

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2.GENERAL

The Stereo-Recorder can be obtained as CHASSIS, WAL-NUT CABINET, and CARRYING CASE models. Here are the applicable codes ( order numbers )

	With 2 Output Ampl.	With 2x2 Loud- speakers	Cod 2-Track	es 4-Track
Wood Cabinet Wood Cabinet Carrying Case Chassis Chassis	X X X	x	1102 1122 1222 1302 1322	1104 1124 1224 1304 1324

Outline and Installation Dimensions, see : S 1

Following codes apply to accessories only :

Output Amplifier (per Channel)	1900
Walnut Cabinet	1950
Carrying case, incl. Cover and 2x2 Loudspeakers	1960

The basic configuration is identical for all models.

A pressure cast aluminum alloy chassis supports the 3-motor drive, one is the electronically regulated capstan motor. All amplifiers are plug-in modules.

An exchange service is organized for the circuit cards. Faulty cards will be exchanged at minimum charge by factory representatives in the respective country. The same applies to etched circuit boards with connectors (control board, regulator, motor control, switch board).

This permits a very efficient service, limiting, in most cases, repair work to finding the faulty module.

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Fig. 2.1-1

2.1. Front Panel, Rear Panel

(Numbering corresponds to REVOX manual)

А	Push buttons

Fast rewind Fast forward PLAY Playback
STOP Stops all operating functions
REC Record (depress simul
- taneously PLAY)

VU-Meters, record pre-selector buttons Record CH I (upper track): Depress left record pre-selector button

Record CH 2 (lower track): Depress right record pre-selector button

Record Stereo (both tracks): Depress both record pre-selector buttons

07 Power switch, tape speed, tape tension
08 Headphone socket ( 200 600 Ohm )
09 Microphone socket, CH 1
10 Microphone socket, CH 2
11 Playback volume control 12 Playback mode switch
12 Playback mode switch 13 Balance control
- Balance control
14 Before-and-after tape switch
15 Record volume control, CH 1
16 Input selector, CH 1
17 Record volume control, CH 2
18 Input selector, CH 2

26 Loudspeaker socket (DIN, 4 16 Ohm)
27 AUXILIARY Input (35 mV)
28 Microphone Input ( .15/2,5 mV )
29 RADIO, DIN connection: Input 2,5 mV Output 1.2 V
30 OUTPUT ( 2.5 V / 600 Ohm )
31 Socket for power cable

Fig. 2.1–3

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General Messurement Conditions: (for voltages in rectangular frames) D.C. Voltages, vertical letters e.g. fr⊡V Meter internal resistance 20 kOhm / V mm. A.F. Voltages: slant letters e.g. + free Meter: Vac, rube or transistor voltmeter 1 MOhm min.

REVOX A77

TECHNICAL DETAILS

Tape transport

Wow and flutter : (weighted)

Tape spool diameter Operating position

Eromional retrieves

Distortion via tape. at 1 kHz peak level and at 0 VU respectively

Equalization

Signal to noise ratio, via tape. weighted as per ASA A Cross talk at 1 kHz :

leave and the set of the set

.....

5 - pole DIN Cinch Outputs per channel : Cinch 5 - pole DIN Isch

Jack Remote control

Output amplifiers : Output power (8 Ω load)

(812 load)

Built in loudspeakers (portable model)

. is is a construction of etc.

Mains voltages

Weight :

____

Measured with REVOX 801 tape 3 motor desc. Elastonically governed capstan motor. Electronic speed change 3 314 and 7 1/2 (ps ± 2.%) mox. + 0.6 % kar 7 1/2 (ps mox. ± 1, % at 3 3/4 (ps less than 2.% max. 10.5." Horizontal or vertical Equipped with silicon transutors throughout. Plug-in printed circuit cards 80 Hz = 2.0 Hz/z ± 2/-3 dB 80 Hz = 2.0 Hz/z ± 2/-3 dB 80 Hz = 2.0 Hz/z ± 1.5 dB 81 at 3.7 1/2 (ps 80 Hz = 2.0 Hz/z ± 1.5 dB 81 at 3.3/4 (ps 7 1/2 (ps mox. 2.% or 0.6 % resp. Record + NAB Playback NAB and IEC (avitohable) 7 112 (ps mox. 63 dB (4 track mm. 52 dB) 3 314 (ps mx. 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 314 (ps mx . 63 dB (4 track mm. 52 dB) 314 (ps mx . 63 dB (4 track mm. 52 dB) 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 4 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 3 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track mm. 52 dB) 5 (ps mx . 63 dB (4 track

Microphone, switchable LO/HI LOW: 50 600 Ω .15 mV HIGH: up to 100 kΩ 2.5 mV RADIO: 33 kΩ 2.6 mV AUX: 1 MS2 35 mV 00 Ω .15 mV OUTPUT max, 2.5 V / Rs 600 Ω .15 mV PHONES 200 600 Ω .12 mV .12 mV

HONES 200 600 Ω

Plug - in optional Music power 20 W (10 Wper channel ) Continuous power 16 W (8 W per channel ) Distortion better than 1 % 4 - 16 Ω Two loudspeakers per channel (automatically disconnected when a plug is inserted into the DIN loudspeaker sockets)

54 transistors, 32 diodes, 4 silicon rectifiers 1 photo resistor, 4 relays Electronically stabilized 101 130 tso 200 occ. 200 // 200 million

Without output amplifiers 70 W With output amplifiers approx. 70 100 W 220 - 250 V~/ 5 A

220 - 250 V~/.5 A 110 - 150 V~/ 1 A Approx. 34 lbs.

We reserve the right to make technical alterations In the interests of technical improvements

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Dimensions Carrying Case

-21 1/4

Dimensions Chassis

Color Code :

red	= red	- rouge	vio	= violet	violet
org	= orange	orange	brn	= brown	— brun
yel	= yellow	– jaune	gry	= gray	– gris
grn	= green	– vert	blk	= black	— noir
blu	= blue	– bleu	wht	= white	blanc

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3.DISMANTLING

Table of Wire Colors

red	=	red	_	rouge		Rot
org	=	orange		orange	—	Orange
yel	=	yellow		jaune		Gelb
grn	=	green	—	vert		Grün
blu	=	blue		bleu		Blau
vio	=	violet		violet	-	Violett
brn	=	brown		brun		Braun
gry	=	gray		gris	-	Grau
blk	=	black		noir		Schwarz
wht	=	white		blanc		Weiss

3.1. Removal of Housing

Set instrument face down on soft basis. Remove remote control dummy plug.
Remove housing fasteners. Pull housing carefully upward. Disconnect loudspeaker connectors on regulator card (fig. 3.9 – 13) in the carrying case.
Reinsert remote control plug.
Bridge power disconnect jack ( 2-pole protective disconnector ) with two insulated banana plugs.

3.2. Removal of Cover Panel
Tilt access lid down. Pull off head cover.
Undo screw A (fig. 3.2 4). Pull cover panel off (Upper rim, 3 retainers).

Fig. 3.2-4

3.3. Removal of Front Panel
Undo screws B ( fig. 3.2 4 ). Pull out power switch knob as well as all rotary knobs and discs. Save retaining ring of power switch.
Pull up monitor panel (4 retainers).

3.4. Removal of Power Switch

Disassemble retaining ring of slide switch ( equalization switch )
Unfasten 3 screws. Remove power switch carefully.
Take off plug connectors.

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3.5. Removal of Brake Unit

Remove cover panel per 3.2.
Remove reel plates (3 screws each).
Brake drums: Undo center screws A (fig. 3.5-6), loosen brakes and lift drums carefully upward.

Be careful not to kink brake bands. Don't touch brake linings, Grease traces reduce braking effect.

Remove connections B (fig. 3.5 -6).
Separate cable bundle (shielded wires) at C (fig. 3.5 6) Remove 3 chassis screws D (fig 3.5 6) and lift chassis
carefully out.

3.6. Removal of Reel Motors
Remove brake drums per 3.5.
Remove frame screws E ( fig. 3.5-6 ).
Unplug output amplifiers ( if present ).
Unplug motor cable connectors; right reel motor, regulator card (fig. 3.6–7); left reel motor, control card (fig. 3.6–8).

Remove 4 reel motor screws F each (fig. 3.5 – 6) and lower motors carefully.

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3.7. Removal of Capstan Motor

Remove output amplifiers ( if present ).
Disconnect capstan-motor and pick-up cables; connections are on control card (fig. 3.7 –9).

Note:

For improved signal to noise performance, the capstan motor connections may be reversed on some recorders in the following manner: E3 = gry, E4 = yel, E5 = grn. Carefully note wire colors before disassembling.

Undo cable clamps A (fig. 3.7 – 9).

Remove cover and monitor panels per 3.2. and 3.3.
Unscrew motor fasteners B (fig. 3.7 10) on headblock. The other screws on headblock shall not be touched as they retain the headblock itself.
Remove capstan motor carefully downward. Guard absolutely against bumping (axis run-out is better than .001 mm = 40 micro inch 1)

3.8. Removal of Control Board

Remove cover and front panels per 3.2. and 3.3.
Undo screws A( fig. 3.8–11). Pull control board down ward.
Remove connectors as needed.

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3.9. Removal of Power Transformer

Remove output amplifiers ( if present ).
Disconnect brake solenoid cables ( unsolder ) per fig. 3.5 –6, B.
Disengage cable to right-hand reel motor on regulator board (fig. 3.6 –7).
Disengage cable to capstan motor and pick-up on motor control board (fig. 3.7 –9).

Note:

Unscrews transformer fasteners and remove entire assembly carefully downward.

Pull off circuit cards and corresponding connectors as needed (fig. 3.9 - 12 and 3.9 - 13).

3.10. Removal of Amplifier Cards
Mark record and playback amplifiers before removing. The amplifiers have to be reinserted in their respective places to maintain correct level settings.
Remove cover panel on the front side and pull amplifier cards.

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3.11. Removal of Potentiometer

Unsolder wires.
Unscrew fasteners from below (fig. 3.11 15)

3.12. Removal of Switch Board (fig. 3.12 -16)

Remove plug-in amplifiers ( fig. 3.10 ).
Remove pusher mechanism (screws A).
Remove shield (screws B).
Remove reset spring C (tape lift lever ).
Connectors: disengage headblock-VU-meter board.

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Remove power switch retaining rings and fasteners D. Lower power switch carefully (avoid linkage rod). Disconnect all terminals on the switch board (fig. 3.12 - 17).
Unscrews 5 fasteners E (fig. 3.12-16) and remove complete assembly forward
Disengage remaining VU-meter connections.

Position of the equalizing slide switch has to be checked at reassembly. Adjust screws F (fig. 3.12 – 16) if necessary (see also 5.1.).

Observe, furthermore, that pressure roller is in rest position ( trip lever of playback cut-off contact S 5, left of release lever ).

3.13. Removal of Frame (Removal of Rotary Switches)

Unscrew VU-meter carrier; lift off carefully ( observe playback cut-off contact S 5 behind VU-meter board ).
Pull connectors from Jacks. (fig. 3.13–18).
Unscrew rotary switch fasteners from above. Disconnect ground strap ( brown ). Remove carrier.

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The three-motor drive assures almost maintenance-free service of the mechanical section. Adjustments and measurements are limited to the few movable parts.

Special tools needed :

Retaining ring pliers

Spring scales or contactors 200 g (7 oz. av), 2000 g (4.4 Ib. av).

Fig. 4.1—19

4.1.1. Tapeguides (fig4.1 -19)

Clean tape guides; don't disturb tape guide A ! To remove tape guide A, unscrew only the fastener to the block ( near upper end of capstan axis ).

4.1.2. Head Mounting (fig. 4.1 – 20)

Record and playback heads are mounted on a common base plate which is fastened in turn to the headblock with 3 screws A.

Don't disturb setscrews D (height adjustment). The heads can be removed while base plate is off (fastening E). If height adjustment is required after change, the respective setscrews D are turned by a like amount front and back.

З	=	Azimuth	adjustment,	record head	(per 6.5.1.)
2	_	Azimuth	aujustment,	record nead	(per 0.5.1

C = Azimuth adjustment, playback head (per 6.3.1.)

4.1. Headblock

Page 15

Once adjustments are made on the headblock, the loosened screws must be resecured with lacquer.

Note:

For improved signal to noise performance the connections to both playback head channels may be reversed on some recorders from the wiring shown in Diag. 3, in other words the colored conductors will be soldered to the right-hand terminal. When replacing heads, re-wire in the same manner.

4.2. Tape Tension

Cover light at the optical end-of-tape switch. Measurement values are taken on a core of diameter
115 mm (4,5 ").
Load and lock empty reel.
Wind several turns of thread on empty reel and pull thread off slowly in the sense indicated, resulting in the following values:

Fig. 4.2-21

Function	7.5 ips or 3.75 ips	А	в
PLAY	tape tension, high	70 gr ( 2.5 oz.av )	85 gr (3 oz.av)
PLAY	tape tension, low	30 gr ( 1 oz.av )	50 gr ( 1.75 oz.av )
		210 gr ( 7.4 oz.av )	about 20 gr (.7 oz.av)
	1	about 20 gr (.7 oz.av)	230 gr (8.1 oz.av)

Check operating voltages of reel motors and phase shift capacitors if these values aren't attained; see table 5.9–46 and section " Modifications " per 8.1.( Rewind).

4.3. Brakes (Stop)

The stop brakes are effective with solenoid de-energized. – Push STOP button.

4.3.1. Brake Torque Measurement

Preparation for measurement per 4.2. Correctly set brakes have following torques:

4.3.2. Brake Adjustment

Check brake system if above mentioned torques are not reached. Brake linings and bands must be absolutely clean and free of greese. Brake bands must be devoid of kinks and lay up full-width on lining.

Details on the modified brake system (brake return spring attached to both ends of the brake-band) are shown on page PL 7a of the parts list. Brake mechanism and solenoid stroke are reset after exchanging band and/or linings.

Page 16

Loosen brake manually ( push in solenoid core ).
Check if both brakes clear simultaneously; if not unscrew the 3 chassis fasteners partly, slide chassis around till both bands are clear.
If necessary, bend one brake adjustment lever.

The solenoid has to be energized for adjustment.

Cover light at the optical end-of-tape switch.
Depress " Reel Motors off " (42), depress button ≪ (fast rewind).
Loosen fastening of solenoid and reset so that the bands clear rollers by from .1 -2 mm (.040" to .080")
Secure solenoid during this adjustment. Braking torque can be varied by hooking springs at different places on the brake adjustment lever.

4.4. Pressure Roller

The pressure lever is actuated electromechanically. Pressure is set by the variable spring force (fig. 4.4 – 25).

4.4.1. Pressure Measurement

Load tape with 1 kHz record
Switch on PLAY.
Tie nylon thread to pressure roller axis ( or to a pin affixed thereto )
and pull with a spring scale (or contactor) in sense A till sound volume drops noticeably.
The spring scale must show 1.5 kg (3.3 lb. av).
Screw C sets pressure force.

4.4.2. Pressure Solenoid Readiustment
Switch instrument to PLAY. If no tape is loaded, cover light at optical end-of-tape switch.
Slide pressure solenoid to the right gap B (fig. 4.4–25) is .3 mm (.012")
Block pressure solenoid.
Check if solenoid core is in end position. The core shall not move if the lever is pulled slightly from the capstan axis.
Secure fasteners of solenoid with a drop of lacquer.
Check pressure, reset screw C if necessary.

4.4.3. Exchange of Pressure Roller

Hold pressure roller axis at groove from above (fig. 4.4 25) and remove bolt fastening E to the side.
Pull pressure roller axis up and roller to the side. Reassembly is explained in the replacement parts list.

Make sure that no cleaning fluid gets to the sintered bearing while cleaning the roller.

4.4.4. Pressure Lever Readjustment

After exchanging the pressure lever, it is necessary to readjust it with respect to lever F (fig. 4.4–25). When the lever is stopped (solenoid core fully out), the distance between capstan axis and pressure roller shall be 10 mm (.4 ").

Page 17

ATTENTION

Capstan Motor with Sleeve Bearings Modification effective from serial Nr. S 60483 G 78003 see section 8.6./page 35

4.5 Capstan Motor (with Ball Bearing) Fig. 4.5.-26

(Control circuitry see 5.10 & 6.2.)

The capstan axis goes completely through the motor. It is held by a sintered bronze bearing (D) and below by a ball bearing. Both bearings are lubricated for their life and should normally require no service. Capstan axis and ball bearing can be exchanged very easily. A defective sintered bearing is to be sent to the nearest factory representative. (Disassembly see para 3.7.)

4.5.1 Removal of Capstan Axis Ball Bearings

The capstan motor need not be removed to get axis and bearing out.

Unfasten securing clip A. Lower capstan rotor.
The axis can be taken out through the top if the tape guide between playback head and capstan axis has been screwed off ( don't disturb quide setting ).
If the retaining ring B is removed, the capstan axis can be lowered with bearing C.

Bearing C is a special tight tolerance part and shall be exchanged only with an original bearing.

Special care must be taken with handling the capstan axis and bearings to avoid damage or entry of dust into the precision parts (run-out better than 1/1000 mm = 40 micro - inch ! ).

Instructions for installation of the new no-turn device A in conjunction with old rotors are given on page PL 9 of the parts list.

Page 18

4.6. Exchange of Reel Motor Bearings

Remove reel motor per 3.6.
Remove brass sleve A. Open clip B and retaining ring C with retaining pliers, open only wide enough to pull them away. Lower rotor with axis out of motor frame.

The belleville springs (see parts list PL 8) remain on the shaft.

In addition to sleeves A there are washers D for height adjustment of the brake drum ( reel plate ). Be sure to put these parts on the same motor axis at assembly. The reel motor ball bearings shall exchanged only with original bearings.

4.7. Lubrication

All bearings are lubricated for their life and should normally require no service. They shall be exchanged only with original bearings, in case of malfunction. If the capstan axis is exchanged, the upper felt washer of sintered bearing D (fig. 4.5 – 26) is to be lubricated with some drops MOBIL DTE extra heavy.

4.8. End-of-Tape Switch (Operation: per 5.9.1.)

The light source of the optical end-of-tape switch can be removed by lifting it upward.

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5. ELECTRONICS

The electronic circuitry is divided into groups, plug-in modules for the most part. There are etched circuit card plug-in modules for :

Input amplifier, record amplifier, playback amplifier, oscillator, and record relay. - Output amplifier.

There are several etched circuit boards, rigidly mounted but with plug-on connectors for:

Regulator
Drive control with photoelectric end-of-tape switch.
Capstan motor control.

Block Diagram ( Amplifiers )

The block diagram shows the relationships between the plug- in amplifiers.

Page 20

5.1. Switch Board and VU-Meter Board

( Diagram No. 1.077.435 & 1.077.480 )

(Removal per 3.12)

The switch board carries plug-in amplifiers ( without output amplifiers ), control switches and potentiometers for inputs, balance and volume. The shielded inputs can be plugged on the switch board ( below, left-hand ). Inputs for playback amplifiers as well as outputs for OUTPUT and output amplifiers can also be plugged in ( right-hand ).

The equalization slide switch is controlled through the power switch. It has to be readjusted in case of exchange. This is done with screws F (fig. 3.12 –16).

The switch terminal contact areas for input selector beforeand-after tape switch, and p functions are printed directly on the board. The rotary switches are encased and indexed against misorientation. Check fig. 5. 2. for ase and contact configurations Assembly information is in the spare parts list.

Fig. 5.1–30

Fig. 5.1–31

Page 21

Fig. 5.1–32

The VU-meter board is linked to the switch board by connectors. It carries the preselector buttons for CH 1 and CH 2, they switch the record-erase signals. (Note that the audio signal has to be switched inversely on the record amplifier when neither button is depressed !)

Fig. 5.2-34

The input amplifier card contains the pre-amplifiers for both channels.

Input sensitivity is matched through a stepped variable feedback (d.c. feedback fixed) at the signal source voltages AUXILIARY (35 mV), track transfer (8 mV), RADIO (25 mV), MICROPHONE high (2,5 mV), MICROPHONE low (.15 mV).

Resistor R 406 / R 426 (100K) is bridged or reduced by parallel resistors for this purpose. If R 406 / R 426 is shorted, amplification of the whole stage is A = 460 approx with 1K in parallel A = 20 approx, and without parallel resistor A = 1.2 approximately. Parallel resitors R 316 / R 317 (CH 1) and R 321 / R 322 (CH 2) are on switch board 1.077.435. The output stage configuration has the advantage that the supply voltage can be fully modulated. Output voltage is nominally 50 mVac, but it can deliver up to 6 Vac undistorted.

This corresponds to an overmodulation stability of more than 40 dB. Aside from the overmodulation stability, sensitivity matching of the input stage through feedback has the advantage in that input noise is not worsened by the series-connected voltage divider.

The record amplifier cards contain an equalization preamplifier ( 0 501, 0 502 ), a VU-meter amplifier ( 503 ), and a driver amplifier ( 0 504, 0 505 ). At the input of the equalization preamplifier is a bus voltage level of about 25 mV ( at 1 kHz and nominal input signal, record regulator fully opened ).

Page 22

Recording is equalized per NAB standard. Lows equalization (3180 ysec) is accomplished by feedback through series-connected C 504 and trimpotentiometers P 501 and P 502. Highs equalization can be set separately for both speeds; P 502 for 7.5ips, P501 for 3.75ips.

Trimpot P 503 serves for voltage balance. The driver amplifiers are laid out for high overmodulation stability. Transistor Q 505 supplies the necessary collector d.c. to Q 504 for modulation.

Q 505 represents high impedance for AF which furnishes the entire output a.c. for modulating the record head. Modulation reserve is better than 15 dB. A tank circuit with a resonant frequency of 38 kHz causes current depending feedback in the emitter circuit of the driver stage ( L 502 / C 514 ) for pilot carrier remainders which could interfere with the erase frequency. Between the decoupling point and record head is another tank circuit for the bias of 120 kHz ( L 501 / C 517 ). The decoupling point is shorted by the record relay during playback.

Amplification of the VU-meter stage can be calibrated on P 504.

To protect the VU-meter indicators against RFI (radio frequency interference), resulting in misindication, the stage is decoupled for RF with C 508.

Fig. 5.4-36

The push-pull collector circuit guarantees minimum odd harmonics. Symmetry of sinusoidal waves is assured and interfering d.c. components can't arise. Erase and bias of 120 kHz is high enough to prevent their interfering. The erase frequency is symmetrically decoupled. In mono-operation, load is held constant by the compensation coil ( para 5.5. ) which proves advantageous for voltage and frequency stability.

Bias current can be set with trimpots P 707 to P 710 separately for CH 1 and CH 2 as well as for both tape speeds.

Purpose of the record relay with an electronic switch is to turn on the oscillator " softly ". To get an integral curve of the switching voltage, Q 601 ( switching transistor ) is delayed by an RC - network ( R 603, C 602 ).

Fig. 5.5.—38

C 602 is discharged at the start and the base of Q 601 is at OV. If contacts 213, 5/6 of record relay REL 601 close, bias voltage rises with the charge on C 602 till saturation. When contacts 213, 5/6 open, C 602 discharges over R 602.

The head compensation coil has two winding halves acting as dummy load for the inactive half of the erase head during mono-operation. The compensation coil balances out inductive strays of the erase head.

Resistor R 604 corrects Q - factor and assures minimum voltage jump between monaural and binaural operation (exchange of erase head may require resetting).

5.6. Playback Amplifier (1.077.720)

Page 23

Playback amplifier cards each contain one playback ( pre-) amplifier and one drive amplifier. The playback head is d.c. coupled to the input stage ( Q 801 ). D.c. feedback from the emitter voltage divider of stage ( Q 802 ) goes over the playback head to base ( Q 801 ) and stabilizes its quiescent point. The feedback current is less than 1 µA which avoids magnetization of the playback head. AF-components of the feedback are shunted through C 803. Its capacitive resistance becomes effective at very low frequencies ( less than 20 Hz ) so that these frequencies are fed back. Playback equalization is switchable NAB - IEC ( CCIR ). The equalization circuit is in the feedback branch collector Q 802 / emitter Q 801. The RC-member R 808 / C 805 / takes care of the lows equalization (3180 psec ).

Basic time constants of equalization are obtained by shorting the partial resistors of the circuit. For :

7.5 ips	NAB	(50 psec)	3 - 4 - 5
	IEC	(70 µsec)	3 - 4
3.75 ips	NAB / IEC	(90 psec)	4 - 5

At the pre-stage exit is a 120 kHz tank circuit for the bias frequency and trimpot P 801 for setting the level of the bus voltage. The signal is conducted over the beforeand - after - tape switch, volume control, and playback mode switch (channel selector) to the drive amplifier.

The drive amplifier is three-stage d.c. coupled. It amplifies the signal to the level of the terminals OUTPUT, headphones, as well as for the modulation of the plug-in power amplifiers. D.c. feedback, emitter voltage divider Q 804 / base Q 803 stabilizes the quiescent points of all three stages. Balance regulation is accomplished with potentiometers P 303, P 304 ( coupled ) in feedback branch emitter Q 805 / emitter Q 803.

In STOP position, when the pressure lever is at rest, output of the playback pre-amplifier (13) is shorted through contact S 5 ( switch board 1.077.435 ).

5.7. Power Amplifier

(1.077.850)

Fig. 5.7—40

The power amplifier cards have separate rectifiers and filters for each channel. The power transformer has two separate windings (32 Vac) for the power amplifiers. The entire amplifier is d.c. coupled and works with a single-ended push-pull output stage. The loudspeaker is, practically free of d.c., in the diagonal of a bridge formed by Q 905 and Q 906 as well as the electrolytic capacitors C 907 and C 908. Q 901 and Q 902 operate as voltage amplifiers.

Series connected D 901, R 911, D 902 are used to keep the no-load current of the output transistors constant, independent of temperature. By strong d.c. depending feedback (100 %), collector Q 906 emitter Q 901, the zero point of the loudspeaker output is held constant. AF-amplification is set by the voltage ratio R 905 to R 906.

5.8. Power Supply

(Diagram Tape Drive 1.077.100, No. 1.077.540)

(Removal, per 3.9.)

Both lines of the power supply can be switched off (Micro-Switches). In addition there are two break-contacts which disconnect upon removal of the housing. The sectional tape core power transformer has five windings for following units :

Capstan and reel motors:	130 Vac	(150 Vac) with 4 taps
Relay control :	22 Vac	(supply voltage 27 Vdc)
Amplifier supply :	24 Vac	( supply voltage 21 Vdc, regulated )
Output amplifier :	32 Vac	(CH 1)
Output amplifier :	32 Vac	(CH 2)

Fig. 5.8-41

Page 24

Power supply board 1.077.540 carries the output amplifier connectors.

The electronically regulated voltage (21 V) for amplifiers (and oscillator) is adjusted at P 106. The transistor Q 102 acts as a series regulator, whose conductivity is controlled by Q 101. The zenerdiode D 104 provides a 12 V reference for the emitter of this latter transistor.

Diode D 103 protects the base-emitter diode of transistor Q 101 from overload in case of possible short circuit in the amalifier section.

5.9. Drive Control

(1.077.370, Diagram Tape Drive 1.077.100)

(Removal per 3.8.)

Fig. 5.9-42

The drive push buttons operate contacts on control board 1.077.370. Remote control contacts can be paralleled to these contacts ( remote control contacts F3 to F10 ). To have a minimum of relays, their control is locked by diodes. The principle of their control is explained by an example for better understanding. In the circuit of fig. 5.9 –43, relay A is energized and contact a 8/12 ( self-holding ) is closed. This corresponds to mode PLAY. Relay B is without current, contact b 6/10 is open.

If button << is depressed, relay A is shorted and drops off. Simultaneously relay B is energized and holds itself over self-holding contact b 6/10. Self-holding can be interrupted by the STOP button or by the photoelectric end-of-tape switch. The following table indicates which relays and solenoids are energized for corresponding functions.

Table 5.9-44

	A	В	С	Record Relay	Roller Solenoid	Brake Solenoid
STOP
PLAY	x				×	x
>>			х			x
<<		x				х
REC	x	x		x	x	x

To avoid loose tape loops at record and playback starts, the right-hand reel motor receives elevated voltage for about 0.3 sec ( winding reversal voltage 105 V ). Relay C must be energized a short period for this, accomplished by the following circuit :

Fig. 5.9-45

Page 25

If the instrument is in the STOP mode, relay A is without current and contacts a 12 and a 11 are in rest position (fig. 5.9 –45). If relay A is energized (PLAY mode), it will hold over self-holding contact a 8/12. Contact a 7/11 closes. A charging current to capacitor C 111 flows over the relay. This energizes relay C and switches the right-hand reel motor to 105 V over contact c 5/9 (self-holding relay C is interrupted by contact a 12). The charging current falls with increasing charge on C 111 and relay C drops off. When switching back to STOP mode, contact a 7/11 opens and capacitor C 111 discharges over the windings of brake and roller solenoids.

The following table summarizes motor voltages for the drive modes.

	Motor Voltages in Vac
Mode	Rewind Motor		Winding Motor
	O	0	O	0
PLAY/REC	55-6 = 49	42-6 = 36	55	42
>>	21		1	05
<<	99		1	5

Table 5.9-46

5.9.1. Photoelectric End-of-Tape Switch

The working current loop of the relays is closed over the self-holding contacts, the STOP button and the collectoremitter path of switching transistor Q 112. Triggering the end-of-tape switch (Schmitt-trigger) does the same thing as depressing the STOP button.

As soon as light falls on photoelement R 155, its resistance drops and base voltage at Q 111 rises. Collector voltage at Q 111 drops and cuts off Q 112.

The process is accelerated by the falling emitter voltage on R 119 (feedback), so that a pulse-type transcient occurs despite the gliding resistance change of R 155 ( sensitivity inertia ).

The trigger conditions light - dark, generate the following voltages at collector Q 111: light, 1 V; dark about 22 V. To check the photoresistor, for light and dark values, it must be disconnected from the circuit. Connections FH1 / FH2 (green) on switch board (fig. 3.8 -11) have to be pulled for this. The resistances are: light, less than 2 kOhm; dark more than 20 kOhm.

(Don't solder at the soldering terminal of the photoresistor, it is heat sensitive).

5.10. Speed Regulation, Capstan Motor (7.077.725)

(Removal per 3.9.)

The electronically regulated tape drive of REVOX A77 uses a method unknown so far in tape recording. That is why this technology of regulation is described here rather detailed. Checks and adjustment of the regulation electronics are done per 6.2.

The capstan motor speed is electronically measured and continously regulated. The driving element is a robust and unpretentious asynchronous motor, whose homogeneous outer rotor generates a minimum of torque pulses, reflected in scant wow or flutter.

To measure the speed, a 120-teeth high-precision gear is cut into the outside surface of the rotor. They are inductively counted by a special pick-up head. The speed is then transformed into a proportional frequency which is analyzed for momentary value in an electric circuit. Any deviation from the nominal, 1600 Hz for 7.5 ips and 800 Hz for 3.75 ips, is detected as to magnitude and sign, and changes the voltage applied to the motor.

The actually regulating network (fig. 5.10-49) consists of a bridge rectifier in series with the supply, whose diagonal is loaded more or less by a power transistor. A power transistor with nearly constant base current doesn't show a genuine resistance characteristic (I - V), for it acts as current control element.

Page 26

Fig. 5.10-49

Circuit 1.077.725 consists of tachometer signal amplifier (Q 201 to Q 205), the discriminator, and d.c. amplifier with power stage (Q 206 to Q 209). The tachometer signal amplifier amplifies, makes symmetrical and limits the pick-up frequency to supply square wave pulses to the discriminator. D.c. dependent feedback stabilizes the quiescent points of the amplifier stages. The discriminator consists of an LC-series-resonance circuit of utmost constancy due to type of circuit and components used. Best drift characteristics are essential to guarantee the required maximum speed variation of .2 % !

The discriminator frequency can be changed from 1600 Hz to 800 Hz by switching in capacitor C 207. In addition, diode D 201 is polarized in conductive direction, thus requiring at the control side but one low current contact, it also decouples the control line ideally.

The discriminator is temperature compensated along with the entire circuitry. Fig. 5.10 –51 shows the typical thermal characteristic of the whole system, measured inside the climatic chamber while motor was running.

Fig. 5.10–51

The signal, delivered from the discriminator, is stripped of a.c. components from the tachometer frequency by integration (C 210 & C 211). The R 215 - C 209 member corrects phase error in the control circuit and improves stability. D.c. amplifier Q 206 - Q 207, whose operating range is shown in the discriminator characteristic, has an amplification of 40 dB. It brings the signal to the value needed for power amplifier Q 209. The phase inversion stage Q 208 has little amplification. Power stage Q 209 consists of a transistor which resists those peak voltages that can occur during cut-off and is able to conduct the power loss, generated during operation, onto the heat sink.

Fig. 5.10-50

Some interesting system data :

1. Steepness of the discriminator and amplification factor of the following amplifier cause the motor voltage to traverse from 0 Vac to the maximum value 130 Vac within 3 Hz frequency deviation at the 1600 Hz tachometer signal frequency. This means that the motor receives full or no voltage for a percentage deviation of ±.1%.
2. Line voltage variations of 20 % cause a deviation in speed of the order of ± .04 %.
3. Variations ± 10 % in operating voltage 21 V, cause a deviation of speed by ±.1 % (operating voltage is additionally regulated).

Page 27

Changing the supply frequency from 50 to 60 Hz varies motor speed by less than .05 %.

Point 4 shows that the supply can be alternated between 50 and 60 Hz with absolutely no changes in circuitry. The new motor is considerably lighter than synchronous motors were to date. It has neither flywheel mass nor a soft clutch. The capstan axis is rigidly fixed to the rotor, making interchanges very easy. The relatively low speeds of the capstan motor ( 400 and 800 rpm ) provide a large diameter capstan axis.

Notes

Page 28

6. ELECTRICAL ADJUSTMENTS AND MEASUREMENTS

Measurement Instruments and Aids

Demagnetizing coil
AF-millivolt meter or VTVM (vacuum tube voltmeter)
AF generator
Distortionfactor meter
Oscilloscope or digital counter
Wow and flutter meter
Test Tapes (Reference Tape)

Test tapes per NAB (1965), and DIN Heimton 7.5 ips (1966) and 3.75 ips (1967) are equalized alike for respective speeds.

7.5 ips = 3180 psec, 50 psec test tape DIN 45513 / 19 H (from AGFA or BASF ) or NAB 7.5 ips.
3.75 ips = 3180 psec, 90 psec test tape DIN 45513 / 9 (from AGFA or BASF) or NAB 3.75 ips (90 psec).
Adjustment Tape 4 track (.25 '')

for height adjustment of the magnetic head on 4-track instruments.

All AF and RF measurements are to be taken with shielded cables.

6.1. Demagnetizing
Magnetic heads and tape guides are to be demagnetized before any measurement or adjustment with running tape.

Strong d.c. - magnetization disimproves signal-to-noise ratio and frequency response. It can also permanently damage the test tapes.

6.2. Tape Speed (Regulator Card 7.077.725)

6.2.1. Pick - up Head - Adjustment

The air-gap between pick-up head and rotor shall be .3 - .4 mm (.012" - .016"). Adjustment is correct when a 35 - 50 mV tachometer signal voltage is measured (at 3.75 ips) on connections blu E2 and brn E1 of the regulator card.

6.2.2. Tacho Adjustment

Exact adjustment of the discriminator, respectively of the capstan motor speed, can be accomplished only with a digital counter.

Connect digital counter to blu E2, brn E1.
Switch recorder to PLAY ( with tape in place ).
For 7.5 ips, the frequency must be 1600 to 1601 Hz. Measurement time 10 sec. minimum. Apply corrections to core of discriminator coil T 201.
For 3.75 ips, the frequency must be 800 to 801 Hz (7.5 ips adjustment has to be made first !) - Apply corrections to trimpot P 201.

6.2.3. Tacho Adjustment with Cathode-Ray Oscilloscope

If need be, adjustments can be made with an oscilloscope referenced to the 50 Hz network frequency test point D (diagram 1.077.725) there is (closed to OV) an a.c. signal of 100 Hz of the following shape :

The superposed frequency comes from the regulating system and is 1600 Hz for 7.5 ips, 800 Hz respectively for 3.75 ips.

Measurement is accomplished in the PLAY mode with tape in place. The superposed frequency must remain standing with respect to the base frequency (at 50 Hz network frequency). (Adjustment procedure per 6.2.2.)

6.3. Playback Adjustment

Preparation :

Check regulated supply voltage ( 21 V ). Apply corrections to P 106 t Power Supply Card 1.077.540 ).

Check of Balance Adjustment :

Connect AF-generator to AUX-input.
Parallel the signal voltage on both inputs by bridging the solder terminals of the AUX cinch-connectors with alligator clamp.
Set controls per fig. 6.3-52

Fig. 6.3–52

Supply about 30 mV / 1000 Hz.
Measure signal voltages at the OUTPUT (2 V approx). Both outputs shall have same signal voltages. Apply correction with the balance control for voltage differences at less than 3 dB at the outputs. Check the amplifier channels if the voltage differences are larger.
Don't readjust the balance control. .

Page 29

6.3.1. Azimuth Adjustment, Playback Head, Coarse (Max. Level)

(Assembly and coarse adjustment after head exchange per 4.1.2.)

Check of gap centering with respect to polished face :

Mark polished face with grease pencil. Let tape run short time. The gap must be in center of worn area.
Set controls per fig. 6.3 -53.

Fig. 6.3-53

Load 7.5" test tape and advance to azimuth adjustment portion (10 kHz).
Connect AF-millivoltmeter to an OUTPUT terminal.
Switch to PLAY and set output voltage to a maximum with screw C (fig. 6.3 54).

6.3.2. Azimuth Adjustment, Playback Head, Fine ( Phase Method )
Set controls per fig. 6.3-55.

Fig. 6.3-55

Switch to PLAY and set output voltage to a maximum (sharp) with screw C.
Secure screw C with a drop of lacquer.

6.3.3. Playback Level from Test Tape

- Set controls per fig. 6.3-56.

Fig. 6.3–56

AF-millivoltmeter remains connected to one output ( 3 V range ).
Advance test tape to level portion.
Set playback mode switch to CH 1.
Set output voltage 2 V with trimpot REPR LEVEL CH1 (fig. 6.3 – 57).

Set playback mode switch to CH 2.

- Set output voltage 2 V with trimpot REPR LEVEL CH 2.

6.3.4. Frequency Characteristic, Playback (from Test Tape)
Set controls per fig. 6.3.-58.

Advance to frequency run portion of DIN or NAB test band.
AF-millivoltmeter, range 300 mV (-20 dB).
Both channels can be measured simultaneously by changing back or forth between each frequency section (CH 1 / CH 2).
It is absolutely essential to accomplish the coarse adjustment per 6.3.1. before using this method to avoid phase errors larger than 90°.

Page 30

6.4. Oscillator and RF - Adjustments

6.4.1. RF - Voltages and Frequency Checking

- Set controls per fig. 6.4 - 59

Fig. 6.4-59

- Load tape and switch to RECORD (STEREO).

A. – Measure erase head voltage against ground with VTVM at VU-meter board (fig. 6.4 – 60) orange HB3 (CH 2) and blue HB6 (CH 1).

2 Track = 21 Vac each
4 Track = 16 Vac each

B. Oscillator Frequency
Load tape, switch to RECORD (STEREO). Pull out lamp at optical end-of-tape switch if measuring without tape.
Oscillator frequency is measured with digital counter or oscilloscope. The frequency is 120 kHz (± 5 kHz) and is measured at orange HB3 and blue HB6 (fig. 6.4 -60) against ground. (Oscilloscope: 12 oscillations per 100 μsec).

6.4.2. Dummy Load

The dummy load compensation is needed only when the erase head is replaced (balance of inductive strays from the erase head during MONO - operation ).

Load tape, switch to RECORD.
Connect digital counter or oscilloscope to blue HB6 ( fig. 6.4 60 ).

Measure RF-frequency in stereo mode.
Disengage record pre-selector CH 2 and balance DUMMY LOAD till same frequency is reached as in stereo mode.

Depress record pre-selector CH 2 and disengage CH 1. Connect oscilloscope or digital counter to orange HB3. Correct DUMMY LOAD if necessary.

Repeat adjustment procedure until any remaining frequency deviations are symmetrical around the nominal frequency ( e.g. CH 1 + 1 kHz, CH 2 - 1 kHz ).
6.4.3. RF Traps, Record
Set controls per fig. 6.4-62

Fig. 6.4-62

Load tape, switch to RECORD (STEREO).
Connect VTVM to test point C 515 of the respective record amplifier (fig. 6.4 – 63), see also diagram 1.077. 705.

Fig. 6.4.–63

Page 31

Set minimum voltage at BIAS TRAP CH 1 and CH 2: Less than < 300 mV (fig. 6.4 - 64).</li>

Fig. 6.4-64

6.4.4. RF - Traps, Playback

Under same conditions as 6.4.3. but, connect VTVM to OUTPUT terminals CH 1 and CH 2 and set BIAS TRAP of playback amplifier to a voltage minimum : Less than 50 mV (fig. 6.4 - 64).

6.5. Record - Adjustments

Preparations :

Following measurements (6.5.1. to 6.5.6.) are to be taken with a record level of - 20 dB below full modulation level. (To avoid over-modulating high frequencies).

- Set controls per fig. 6.5 -65.

Set AF-generator to 10 kHz (see 6.5. preparations).
Load tape and switch to RECORD.
Adjust for maximum signal with screw B (fig. 6.5 67), (turn slowly - indication delay !).

Fig. 6.5–67

6.5.2. RF - Bias

Since the high frequency playback voltage is bias dependent in a curve with distinct maximum, a relationship which can be used to determine the operating point (fig. 6.5 – 69). The measurement is per 6.5.1, (10 kHz, -20 dB).

Controls OSCILLATOR CH 1 and CH 2, 3.75 and 7.5 (fig 6.5 –68) are turned from the left limit in clockwise fashion until maximum AF output voltage is reached (playback mode switch by choice CH 1 / CH 2).

REC.

Fig. 6.5-65

Connect AF-millivoltmeter to OUTPUT terminal.
300 mV range
Adjust AF-generator (3 4 mV) at 1000 Hz to obtain 200 mV at the OUTPUT terminal (voltage as for playback from test tape per 6.3.3, but 20 dB lower).

6.5.1. Azimuth Adjustment, Record Head, Coarse

- Set controls per fig. 6.5 -66.

Fig. 6.5–66

Fig. 6.5–68

Note the pointer deflection at the maximum and continue turning in the same sense till AF-output voltage has dropped by the amount ( $\Delta\V)$ shown in the following table.

Page 32

Type of Tape	∆V - 3.75 ips	∆V - 7.5 ips	∆V-15 ips
AGFA PE 31	4 dB	3 dB
REVOX PE 36 RX REVOX 207 REVOX 601 AGFA PE 36 BASF PES 35 (LH) SCOTCH 202/203	5 dB	4 dB	2 dB
SCOTCH 150/215	5 dB	5 dB
REVOX 621	4,5dB	4dB	2dB

Table 6.5-69

6.5.3. Azimuth Adjustment, Record Head, Fine

Set controls per fig. 6.5 - 70

Fig. 6.5–70

The balance regulator must be set accurately (per 6.3, preparations).
Other conditions as up to now (Record, Stereo, 10 kHz, 20 dB).
Set output voltage to a maximum (sharp) with screw B (fig. 6.5 67) turn slowly indication delay !).
It is absolutely essential to accomplish the coarse adjustment per 6.5.1. before using this method to avoid phase errors larger than 90°.
Control possibility :

Pass through lower frequencies with sound generator Output voltage shall remain constant.

- Secure setscrew with a drop of lacquer.

6.5.4. Record level

- Set controls per fig. 6.5-71

Playback level (per 6.3.3.) and balance adjustment (per 6.3. preparations) must be set.
AF-generator to AUX-input (connect in parallel ).
AF-millivoltmeter to one OUTPUT terminal, range 300 mV.

Load tape, switch to RECORD (Stereo).
Before-and-after-tape switch to INP. Supply 1000 Hz from AF-generator, set generator level such that OUT-PUT terminal voltage is 200 mV.
Switch to NAB and adjust REC LEVEL trimpots (fig. 6.5–72) to obtain 200 mV at OUTPUT terminal, playback mode switch to CH 1 or CH 2 respectively.

Fig. 6.5–72

6.5.5. Record Equalization

Switch AF-generator at samevoltage (-20dB) to 12 kHz. Set controls per fig. 6.5 -71 (NAB).

Fig. 6.5—73

Adjust output voltage from 0 to + 1 dB with trimpots EQUALIZ. ( 0 dB = 200 mV / 1000 Hz per 6.5.4 ). Playback mode switch CH 1 both speeds, likewise CH 2 both speeds.

6.5.6. Frequency Characteristic via Tape

Set controls per fig. 6.5 -71 (NAB).
Calibrate AF-millivoltmeter (change slightly the signal voltage till 0 dB or even-numbered indication is reached).
Measure frequency characteristics 7.5 ips and 3.75 ips (by changing playback function switch CH 1 / CH 2, both channels can be measured, one after the other).
6.6. Distortion Factor Measurements VU-Meter Calibration Noise Measurement Erase Attenuation Crosstalk Attenuation
6.6.1. Distortion Factor (via Tape), VU-Meter Calibration
Set controls per fig. 6.6 -74.

Page 33

Fig. 6.6—74

AF-generator ( 500 Hz ). Switch 20 dB higher with respect to previous setting ( input voltage about 40 mV )
Connect distortion factor meter to an OUTPUT terminal.
Load tape, switch to RECORD (Stereo) 7.5 ips.
Measure distortion factor (CH 1 and CH 2)
Set input level so that the distortion factor is 2 % on the worse channel at 7.5 ips
Repeat procedure with 3.75 ips. Distortion factor may be 3 %. In case of higher values, reduce input level till 3 % distortion factor is achieved.
Distortion factor control "Before-tape": Set before-and after-rape switch to INP. Distortion factor shall be 1 % maximum !
Switch back to NAB lower input level by 6 dB.
Adjust METER CALIB (fig. 6.6-75) with trimpots CH 1 and CH 2, VU-meter indication 0 dB (100 %).

Fiq 6.6—75

6.6.2. Noise Voltage ( and External Voltage ) via Tape

Noise voltage measurements refer to full-modulation (distortion factor 2 % at 7.5 ips, 3 % at 3.75 ips resp. per 661)
To avoid RF-interference errors, a tape erased on the recorder is measured in the PLAYBACK mode.

Effective values (weighted, CCIF filter) of the noise and external voltages can be seen for the REVOX 601 tape in the following table:

	2 T	rack	4 Tr	ack
	7.5 ips	3.75 ips	7.5 ips	3.75 ips
Noise Voltage	> 66 dB	>63 dB	> 62 dB	> 59 dB
Ext. Voltage	> 58 dB	> 57 dB	> 56 dB	> 54 dB

Table 6.6-77

If these noise and external voltage separations are not attained, the tape guide elements and magnetic heads are, once more, to be demagnetized carefully.

6.6.3. Noise Voltage, External Voltage "Before-Tape" ( Check )
Switch recorder to STOP.
Before-and-after-tape switch to INP (fig 66-78).

Fig. 6.6—78

The noise and external voltage separation shall be more than 75 dB referred to full-modulation

Check of Input Amplifier :
Set controls per fig. 6.6 -79
To avoid hum interference during this procedure, the microphone inputs ( jacks or cinch connectors ) are to be terminated with 200 ohm.

The noise and external voltage separations shall be more than 45 dB referred to full-modulation.

Fig. 6.6-76

Page 34

6.6.4. Erase Attenuation

Following Measurements: Erase attenuation, crosstalk, mono and stereo (6.6.4 - 6.6.6.) can be taken with a selective VTVM (band width less than 100 Hz).

To measure erase attenuation, a frequency of about 1000 Hz is recorded and consecutively erased. The record remaining on the tape is then measured.

- Set controls per fig. 6.6 -80

- Record 1000 Hz, full-modulation.

STOP, rewind tape.

Close record volume controls (fig. 6.6–81).

Fig. 6.6-81

Switch recorder to Record and measure the erase attenuation.

The remainders on the tape shall be better than 75 dB under the level of full-modulation.

6.6.5. Crosstalk, Mono (selective per 6.6.4.)

A mono-recording 1000 Hz full modulation is appropriately taken 1 min on CH 1 and afterwards 1 min on CH 2 for this measurement on a factory-tape. Note that the record butt on the unused channel is disengaged.

- Set controls per fig. 6.6-82.

Fig. 6.6–82

Set playback function switch to CH 2, measure the cross-talk separation 1 - 2 and bring with crosstalk compensation trimmer (fig. 6.6 – 83) to best value (more than 60 dB).

Fig. 6.6—83

- Advance tape to recording on channel 2.

Set playback function switch to CH 1, measure crosstalk separation 2 - 1, correct P 305 if necessary.

For strong corrections, repeat crosstalk 1 - 2 measurement and adjust for mean value.

6.6.6. Crosstalk, Stereo (selective 6.6.4.)

Measure and if necessary adjust mono crosstalk attenuation per 6.6.5. before checking the stereo crosstalk attenuation.

Don't disturb P 305 compensation trimmer during the following measurements.

The generator is switched in parallel on the AUX-inputs while measuring stereo crosstalk attenuation. Close the input to the channel to be measured.

- Set controls per fig. 6.6 -84.

Fig. 6.6—84

- AF-generator 1000 Hz, full modulation, record stereo.

Measurement 1 – 2 :

AF frequency millivoltmeter at output CH 2, record volume control CH 1 fully open (at right limit), record volume control CH 2 fully dosed (left limit).

Measurement 2 – 1 :

AF frequency millivoltmeter at output CH 1, record volume control CH 2 fully open (at right limit), record volume control CH 1 fully dosed (left limit).
Crosstalk attenuation shall be better than 45 dB.

Page 35

6.7. Output Voltage Check

- Set controls per fig. 6.7 -85

Fig. 6.7—85

Load tape, switch to Record (Stereo).

AF-generator 500 Hz, full modulation.

- AF frequency millivoltmeter at output CH 1 or CH 2. Output voltage shall remain constant( ± 1 dB ), when the before-and-after-tape switch INP / NAB / IEC and the playback mode switch STEREO / CH 1 / CH 2 / MONO is switched around. If the output voltage doesn't stay within the indicated tolerance, proceed per 6.5.4.

6.8. Wow and Flutter

The values given in the technical data are measured with a wow and flutter meter per Std DIN 45507. Values obtained by a different standard can't be compared.

Page 36

7. ACCESSORIES

7.1. Remote Control

All push button functions can be accomplished by RE-MOTE CONTROL. The remote control cable needs no shielding and its length is not critical. The remote control unit circuitry is per fig. 7.1–86.

REMOTE CONTROL PLUG (HIRSCHMANN WIST 10)

Fig. 7 .1 –86

The 27 Vdc on terminal 7 is for use with slide projectors (load 150 mA maximum).

The dummy connector must be inserted for operation without the REMOTE CONTROL unit (this dummy connector shorts terminals 1 & 2).

7.2. Operation with a Timing Clock

The timing device is to be wired into the electric power feed in a manner which will provide electric current to the REVOX A77 during predetermined intervals only. For operation with a timing clock, the power switch and speed selector remains continuously in the position of the desired tape speed.

Page 37

8. MODIFICATIONS

8.1. Rewind

For bad rewind with 18 cm (7") reels : Replace resistor R 125 (820 Ohm) by resistor 1.2 kOhm, 9 Watt (drive control 1.077.370).

8.2. Switch Noise

The following change can improve the situation where operation of the STOP button out of RECORD and PLAY modes causes clicks :

Ground connection brn (fig. 3.13 –18) is unsoldered from the printed side and resoldered to the ground conductor at playback switch S5 ( switch board 1.077.435 ).

Another improvement results from replacing the diode D 601 (record relay card) by an RC-network: C = 50 µF / 30 V, R = 100 Ohm / 1/8 W (series connected, observe polarity).

8.3. RFI

Interference from strong radio an TV transmitters can be removed by the following measures :

Solder 1500 - 5000 pF ceramic capacitors from ground connection shield ( shielded cable ) to chassis ( tubular rivet of connector fastening ) at the disturbed inputs ( see example C 154 OUTPUT terminal ).

Powerful UHF television transmitters may be picked up by the playback head cables. If an interfering buzz occurs, the following change should be effected in the playback amplifier:

Connect a capacitor of 100 pF (maximum 220 pF) from base to emitter of Q 803 (similar to C 803 on Q 801).

8.4. Transfer Play Sensitivity

Resistor R 316 and R 321 are 10 kOhm in recorders of lot 1. Substitution with 3.3 kOhm resistors ups recording sensitivity (gain 10 dB approx).

8.6.

Capstan Motor with Sleeve Bearings

Modification effective from serial Nr. S 60483 and G 78003

for illustration see parkslist page E 10.

The capstan shaft extends through the full length of the motor and is supported by two sintered-bronze bearings. The lower bearing is designed to restrict the axial movement of the shaft by means of a plastic coated thrust (low-friction) washer. All bearings are lubricated for their life and will normaly not require any service.

Capstan shaft and low-friction washer may be replaced in the field.

If a bronze bearing has become defective, the motor must be sent to the nearest factory service-center. (For disassembly instructions see section 3.7.)

8.6.1.

Removal of Capstan Shaft and low-friction Thrust Washer

Removal of capstan shaft and low-friction washer is possible while the motor remains installed in the recorder.

Carefully remove shaft lock A by pulling it sideways with a pair of angled pliers. DANGER! Do nα attend to pry the lock loose with a screw-driver etc. because it will fly off quite forcefully. Slide off the rotor portion of the capstan motor.
After removal of the tape quide between the playback head and the capstan shaft, the shaft can be pulled up and out of the motor. (Take care not to disturb the setting of the adjusting nut on the tape quide.)
To remove the low-friction washer take out the circlip B with the aid of special pliers. The bearing parts can now be disassembled in the following order: Springwasher E, low-friction washer F and thrust bearing G.
The capstan shaft may now be removed by pulling it downwards and out of the motor.
When re-assembling the lower bearing, apply one drop of Isoflex PDP65 oil to the low-friction washer.

When handling shaft and bearing, extreme care must be exercised, so as to avoid damaging them and to prevent any dust particles from entering the precision bearings. (runout accuracy 1/1000 mm).

8.5. Replacement of Capstan Motor

Starting with Serial Nos. S15500 and G16150 a new type of Capstan-Motor was installed which operates on a 20 V higher supply voltage and therefore requires a modified power-transformer. The voltage appearing at point E8 blu (speed control board 2.077.725) now measures 150 V. When using an old motor in conjunction with a new transformer, a type 40318 transistor must be used in position Q 209 on the speed control board.

Page 38

9. TROUBLE SHOOTING

Pre - Check :	Check network voltage.
	Allowable deviation ( also for short periods ) at respective settings of the voltage selector :
	110 Vac : rnin 96 Vac, max 125 Vac 130 Vac : rnin 112 Vac, max 145 Vac 150 Vac : rnin 130 Vac, rnax 165 Vac 220 Vac : rnin 190 Vac, max 245 Vac 240 Vac : min 210 Vac, rnax 270 Vac 250 Vac : rnin 225 Vac, max 290 Vac
	Use a regulator if the deviations are higher. Note that regulators have a marked leakage field (keep far from recorder).
	Check of regulated supply voltage 21 Vdc. Adjust on P 106 or replace diode D 104, if necessary.

9.1. Faults in the Drive Capstan Motor fails to run :	Check motor capacitor C 151. Check regulation electronics, test points ( diagram 1.077. 725 ).
	If the capstan motor does not start by itself after manual stopping, the regulator pre-amplifier is oscillating. Exchange R 206 { 100 Ohm) against 330 Ohm.
	Check capstan bearings, exchange ball bearings against fac- tory - new original ones.

Capstan motor rumbles :	Exchange bearings against factory - new original ones.
Capstan motor whistles :	Check gap rotor to pick-up (per 6.2.1). Put a strip of rubber or equivalent between pick-up and its mounting surface for vibration isolation.

Tape Speed too low :	Check pick-up separation. Measure pick-up frequency ( per 6.2.2 ). Check regulation electronics, test points.

Page 39

Wow and Flutter :

Mechanical causes :

Periodic wow and flutter whose origin is in a defective pressure roller or whipping capstan axis can be recognized by observing the rotating element's rythm (pressure roller or capstan axis might be marked with felt tip pen). Pressure roller, see also 4.4.1.

If rythm of wow is identical with the rotation of the lefthand reel motor, the origin may be either mechanical or electrical. The mechanical cause may be defective bearing or misadjusted brake.

Electrical causes :

Overly strong counter torque of left-hand reel motor can be cause for wow; check motor voltages, see table 5.9 -46.

If wow occurs only at 3.75 ips, it may have its origin in too large a distance of pick-up or in the regulation circuit, (see 6.2.1).

Wow at both speeds may be caused by a defective capacitor in the RC-network R 215/. C 209 in the regulation circuit. Replace capacitor.

Inadequate Starting Behavior, Slow Rewind :

Reels smaller than 60 mm (2 · 3/8") should not be used if at all possible.

Optimum behavior can be expected only at nominal line voltage.

Check reel motors with loosened brakes for light run (axial play of reel motors .2 to .3 mm (.008 to .012").

Increase R 125 to 1 or 1.2 kOhm.

Push Buttons Don't Hold :

Dummy connector REMOTE CONTROL is missing.

End-of-tape switch is defectife, see 5.9.1, or strong light is incident on photoresistor.

Check relay operating voltage ( 27 Vdc ).

Page 40

Brake Solenoid Doesn't Function :

Check solenoid coil. Clean core. Check relay operating voltage ( 27 Vdc ).

Brakes (STOP) too weak, too strong, irregular :

Check brake bands, check brake lining. Clean and degrease. Measure brake tension per 4.3.

Page 41

9.2. Faults in Circuitry

Pre-Check :	See Pre-Check 9.


Playback Amplifier Hums :	Break in playback head windings.
	Flap shield doesn't close adequately.
	Supply voltage 21 Vdc, hum voltage too high.
	Capstan motor leakage field too high, check supply voltage, 100 Vare max
	Possibly strong interference from UHF-TVtransmitters, see 8.3.
	Line voltage too low, see 9 ( pre-check ).

Playback Amplifier Noisy ( Drive Amplifier )	with closed volume control :
	Defective transistor () 803 or () 804
	Amplification too high from defective balance potentio-
	meter.
	Noisy zener-diode in power supply, replace with planar type.
	Inadequate matching to following amplifier. Open VO- LUME control completely, adjust volume in amplifier.

Playback Amplifier Noisy :	with open volume control :
	Condition: Function PLAY; without tape in place (optical end-of-tape switch: Cover light ); before-and-after-tape switch position NAB / IEC.
	Defective transistor Q 801 or Q 802.
	Check tantalum capacitors.

Recording Noisy :	with closed record volume control :
	Check playback amplifier.
	Clean and demagnetize magnetic heads.
	Procedure with pulled record amplifier, once fault is correc- ted, record amplifier found defective :
	Replace transistor Q 501 or Q 502.
	Check C 515 for leakage current, check tantalum capacitors.
	If fault persists with pulled record amplifier :
	Defective oscillator or erase head - replace.

Page 42

with open record volume control : If noise occurs only with open record volume control, check input amplifier. Check Q 401 / 421 and Q 402 / 422. Check tantalum capacitors. Highs Playback Weak or Variable : Dirty magnetic heads. Tape is not of type pre-scribed by manufacturer. Wrong bias (record equalization), see 6.5.2. to 6.6. Playback head misadiusted, see 6.3.1. Record head misadiusted, see 6.5.1 Worn magnetic heads. No Record : Check relays. Check relay Q 601. Replace oscillator. Dirty erase head. Inadequate Erase : Measure RF-voltage; if it is too low, check supply voltage at oscillator. Defective erase head. Tape extremely over-modulated. VU-Meter. None or Faulty Indication : Defective VU-meter. Calibration misadiusted, P 504 Defective rectifier D 351 - D 354 ( VU-meter board 1.077. 480). Defective amplifier, Q 503 (record amplifier card 1.077.705) Switching Clicks: see Modifications 8.2 see Modifications 8.3. RFI (Radio Frequency Interference):

Transfer Play Sensitivity Too Low :

se Modifications 8.4.

Page 43


NACHTRAG ZU DER EINSTELLANLEITUNG (Kapitel 6)	SUPPLEMENT TO THE ADJUSTMENT IN- STRUCTIONS (Chapter 6)	SUPPLEMENT POUR INSTRUCTIONS DE RE- GLAGE (chapitre 6)
Im Laufe der Zeit erfuhr die A77 diverse Anpas- sungen, durch welche einige Einstellarbeiten nun von den in der vorhergegangenen Anleitung be- schriebenen abweichen. Die Abweichungen sind nachfolgend mit der entsprechenden Seiten- und Kapitelnumerierung versehen aufgeführt.	Over the years, a few adaptations have been in- troduced for the A77. Adjustment work may therefore differ. The following paragraphs re- place or must be added to the indicated page and chapter number.	Le magnetophone A77 ayant subi divers change- ments au cours du temps, il s'est avéré necessaire de modifier certains reglages decrits dans les ins- tructions precedentes. Ce supplement concerne les pages et les chapitres suivants.
Seite 14, Kapitel 4.4.1 Messung der Andruck- kraft	Page 14, Chapter 4.4.1 Measuring the pinch rol- ler force	Page 14, chapitre 4.4.1 Mesure de la force d'ap- pui
Die Andruckkraft bei Geraten mit polierter (glanzender) Tonrnotorachse betragt 1,5 kg, bei Geraten mit sandgestrahlter Tonmotorachse (matt) 1,2 kg.	Pinch roller pressure must be 1.5 kg at polished shafts (shiny), at sandblasted capstan shafts (mat), pressure must be 1.2 kg.	La force d'appui du galet est de 1.5 kg pour les magnetophones ayant un axe de cabestan lisse (briliant) et de 1,2 kg pour ceux avec un axe sable (mat)
Seite 23, Kapitel 5.10 Speed Regulation, Cap- stan Motor	Page 23, Chapter 5.10 Speed Regulation, Capstan Motor	Page 23, chapitre 5.10 Regulation de vitesse du moteur de cabestan
Druckfehler, die Nummer 7.077.725 heisst rich- tig 1.077.725 (nur im englischen Text).	Printing error, the number 7.077.725 should be 1,077.725 (only in the English text).	Suite à une erreur d'impression 4e numero 7.077.725 est 1.077.725 (seulernent dans la ver- sion anglaise).
Seite 25, Kapitel 5.11 Speed Regulation, Cap stan Motor 1.077.724 (neues Kapitel)	Page 25, Chapter 5.11 Speed Regulation, Cap stan Motor 1.077.724 (new chapter)	Page 25, chapitre 5.11 Regulation de vitesse du moteur de cabestan 1.077.724 (nouveau chapitre)
Das gesamte Regelungssystem besteht aus Ton- motor, Regelelektronik und Tachometer zur Drehzahlmessung. In der Eingangsschaltung rnit 1C201 wird die zur Bandgeschwindigkeit proportionale Frequenz in ein Rechtecksignal umgeforrnt. Die nachfoigen- de Frequenzteilerschaltung sorgt für ein exakt symmetrisches Signal. Die negativen Flanken des frequenzgeteilten Rechtecks triggern eine mono- stabile Kippstufe (Präzisionstimer IC202). Durch Unterdruckung jedes zweiten Impulses bei der hohen Geschwindigkeit muss der Motor doppelt so schnall drehen, um dieselbe Triggerfrequenz und cam't dasselbe Signal am Ausoang von	The speed control system consists of the capstan motor, the speed regulating circuit and the tacho head to sense the motor speed. The input circuit with IC201 shapes the speed which is proportional to the frequency into a square wave and the following divider circuit delivers an exactly symmetrical signal. The trailing edges of the square wave are triggering a mono flip-flop (precision timer IC202). When selecting the higher tape speed, every second pulse becomes suppressed, thus the motor has to run with double speed in order to produce the same trigger frequency and consequently the same signal at the output of IC202. The oulse width for	L'ensemble du système se compose du moteur de cabestan, de l'électronique de regulation et de la tête tachymetrique. L'ótage d'entrée (IC201) met en forme le signal provenant de la tête tachymetrique. L'etage sui- vant formé d'un diviseur de frequence donne un signal parfaitement symétrique. Les flancs néga- tifs du signal rectangulaire commandent ensuite une monostable de precision (IC202). La sup- pression d'une impulsion sur deux oblige le mo- teur à tourner deux fois plus vite afin de retrou- ver la même fréquence de commande et le même signal a la sortie de la monostable (IC202). Un réseau RC de precision garantit la stabilite de la

IC202 zu erhalten. Die tmoulspreite wird für 1C202 durch einen hochstabilen RC-Seriekreis bestimrnt. Mit Potentiometer R217 kann die Sollgeschwindigkeit eingestellt werden. Ein Tiefpass bildet den DC-Mittelwert aus dem Rechtecksignal. Dieser wird im nachfolgenden DC-Verstärker, welcher ein Netzwerk für die Stabilität des Regelkreises enthalt, weiterverarbeitet und steuert schilesslich als Gleichspannungswert den Regeltransistor Q205 an. Bei ausseren Drehzahlanderungen variiert das Tastverhältnis des Signals bei Punkt F und somit auch die Steuer spannung fur den Regeltransistor.

Durch das Anlegon einer extornen Roferenzspannung am Anschluss CONTROL VOLTAGE bei IC202 kann die eingestellte Frequenz über einen grossen Bereich verandert werden (variable Bandgeschwindigkeit)

Seite 26, Kapitel 6.2.4 Tachoabgleich 1.077.724

Der Luftspalt zwischen Tachokopf und Rotor soll 0.3 ... 0.4 mm betragen. Die Einstellung ist in Ordnung, wenn an den Anschlussen EI (brn) und E2 (blu) 35... 50 mV (bei der kleineren Geschwindigkeit) Tachometer-Signalspannung gemessen wird.

Page 26. Chapter 6.2.4 Tacho Head Adjustment 1.077.724 (new chapter)

IC202 is determined in a highly stable RC-series

network With B217 the motor speed can be

adjusted to its nominal value. By passing the sig-

nal through a low-pass network, an average DC-

value is derived from the square wave. This DC

potential is further processed in a DC-amplifier.

which contains a network to ensure the stability

of the control loop. The DC-signal then reaches

the base of the regulating transistor 0205. A

variation in motor speed will also vary the duty

cycle at F with a consequent change of the bias

potential for the regulating transistor. By feed-

ing an external reference potential to the termi-

nal CONTROL VOLTAGE at 1C202, the adjust-

ed frequency may be varied over a wide range

(variable tape speed).

The air gap between the tacho head and the rotor of the capstan motor should amount to 0.3 ... 0.4 mm/0.011 ... 0.02 inches. The head is correctly positioned when measuring a signal voltage of 35... 50 mV at lower speed between the connectors E1 (brown) and E2 (blue)

Page 26, chapitre 6.2.4 Reglage de la tête tachymétrique 1.077.724 (nouveau chapitre)

largeur des impulsions delivrees par IC202. La

vitesse norninale se regle avec le potentiomètre R217. Apres le passage dans un integrateur don-

nant la valeur moyenne du signal, celui-ci peut

attaquer un ampli a courant continu contenant

un circuit pour la stabilité de la regulation. Cette

tension continue commande finalement le tran-

sistor de regulation 0205. Une variation ex-

térieure de la vitesse de rotation changera le rap-

port d'impulsions au point E et par consequent la tension appliquée au transistor de regulation.

L'application d'une tension de reference au

point CONTROL VOLTAGE de l'IC202 permot

de varier la vitesse dans une large gamme.

L'espace entre la tête tachymetrique et le rotor du moteur doit être de 0,3 à 0,4 mm. Le reglage est correct lorsque la tension mesuree entre El (brun) et E2 (bleu) est de 35 a 50 mV pour la plus petite vitesse.

Page 44

Geschwindigkeits-Eichung

Tape Speed Calibration

schwindigkeit auf Wiedergabe starten.
Zähler an IC202, Pin 3 (F) und Masse auf Drehzahlregelungs-Steckkarte anschliessen.
Zähler-Anzeigewert gemäss Tabelle A, bei Abweichungen mit R217 korrigieren.
Gerät auf kleine Bandgeschwindigkeit umschalten, die Anzeige am Zähler darf nicht än-

Bei beiden Geschwindigkeiten muss die Anzeige-

and ground (E2, blue wire) located on speed
Load recorder with tape, select high tape
The counter display should be as per table A, correction can be made with R217.
Switch recorder to low tape speed, read-out

At both tape speeds, the indicated frequency must be between ± 1 Hz of the nominal frequen-

Page 27, Chapter 6.3.3 Reproduce Level from

new tape brands that allow quite a higher mag-

netization (test tape playback level by 1000 Hz,

257 nWb/m = 0 VU). Adjust the output levels to

Page 28. Chapter 6.4.1 RF-Voltages and Fre-

RF-voltages differ depending on used oscillator

Réglage de la vitesse
Connecter un compteur entre le point 3 (F) de l'IC202 et le fil bleu E2 (masse) sur la carte
Faire défiler une bande en lecture à grande
Avec R217 régler la fréquence en fonction de la tabelle A
Commuter en petite vitesse: la valeur ne doit
Pour les deux vitesses la tolérance est de 1 Hz.

×.
1		51	2,37	1	4	,75	I		4,75	1	9	, 5	١		9,5	1	1	9	1		19	1	38	1
۱	ip	51	15/16	1	1	7/8	1	1	7/8	1	3	3/4	1	3	3/4	1	7	1/2	1	7	1/2	1	15	1
٠		-1-					-1						-1						-1-					-+
I	Ηz	1		30	0		1		1	40	0		۱			8	00		1		8	00		1
4				-	_		- 4-	-		-	-		- 4			-

Seite 27, Kapitel 6.3.3 Wiedergabepegel ab Test-

eine erheblich höhere Magnetisierung zulassen (Pegeltonteil bei 1000 Hz bezogen auf 257 nWb/m = 0 VU) ändern in der folgenden Einstellung die Pegel. Die Ausgangsspannung (re-CH1/CH2 wird anstelle 2 V auf 1,55 V einge-

Seite 28. Kapitel 6.4.1 HF-Spannung und Fre-

Die HF-Spannungen sind je nach Oszillator und Geschwindigkeit unterschiedlich:

22 V / 120 kHz Oszillator/Oscillator/Oscillateur 1.077.710 (MPA + MPB) 2 Spur/track/pistes ca./approx./env. Oszillator/Oscillator/Oscillateur 1 077 730 (MPA + MPB) ca./approx./env. 18 V / 120 kHz Oszillator/Oscillator/Oscillateur 1.077.795 (Mono) MPA ca./approx./env. 44 V / 120 kHz 800 mV / 120 kHz ca./approx./env. resp. 80 mV / 1 kHz

and tape speed selected:

Seite 29, Kapitel 6.4.4 HF-Sperrkreis Wiederga-Page 29, Chapter 6.4.4 RF-Traps, Reproduce Page 29, chapitre 6.4.4 Circuit-bouchon de lec-Das Spannungsminimum (BIAS TRAP) muss The voltage minimum (BIAS TRAP) must be

smaller than 100 mV

Seite 29, Kapitel 6.5 Aufnahme-Einstellungen

Page 29. Chapter 6.5 Record Adjustments

Der NF-Generator wird bei 1000 Hz so eingestellt, dass am Ausgang OUTPUT 155 mV anste-

Adjust audio generator with 1000 Hz to get a reading at the tape recorder's output of 155 mV.

Page 27, chapitre 6.3.3 Niveau de référence avec

Les nouvelles bandes, permettant un niveau de magnétisation plus élevé, nécessitent un changement du point de réglage. Régler la tension de sortie avec les potentiomètres REPR LEVEL CH1/CH2 à 1,55 V au lieu de 2 V (1000 Hz 257 nWb/m = 0 V(1)

Page 28. chapitre 6.4.1 Contrôle de la tension

La tension doit être inférieure à 100 mV.

Page 29, chapitre 6.5 Réglage en enregistrement

Régler le générateur à 1000 Hz de manière à obtenir 155 mV à la sortie OUTPUT du magnéto-

Page 45

Tabelle umfangreicher geworden:

Bedingt durch modernere Bandsorten ist diese Due to modern tape brands, the table has been Les nouveaux types de bande ont nécessité de enlarged:

Page 30, tabelle 6.5-69

compléter la tabelle:

\| Bandsorte \| Type of tape \| Type de bande	\| _U 9,5cm/s \| _V 3 3/4ips \|	\| _U 19cm/s \| _V 7 1/2ips \|	_U 38cm/s _V 15ips \|
REVOX 601	1 5 dB	1 4 dB	3 dB
REVOX 621	t 4,₅5	4	3 \|
I REVOX 631	6	6	4
I SCOTCH 206	5	5	3
I SCOTCH 207	1 5	4	1 3 1
I SCOTCH 250	5	6	4 1
SCOTCH 256	6	6	4
AMPEX 406	6	5	4
I AMPEX 407	6	5,5	4
AMPEX 456	1 5	6	4 1
I AGFA PEM 368	5	1 5	3,5
I AGFA PEM 468	1 6	6	3,5
AGFA PER 525	6	1 5,5	3
I AGFA PER528	1 6	6	4
BASE LPR-35LH	1 6	5	4
I BASE SPR 50LH	1 6	5,5	3,5
\| BASE LGP 30P	6	5,5	4
\| BASF LGR 50	I 6	6	4
I MAXELL UD-XL	1 6	1 5	4
I TOK AUDUA	1 6	5	4
\| EMI 816/817	6	6	+ I 4

Seite 30, Kapitel 6.5.4 Aufnahme-Pegel

Page 30, Chapter 6.5.4 Record Level

dern 155 mV betragen (siehe Korrektur Kapitel 200 mV (see correction chapter 6.3.3).

Die Ausgangsspannung sollte nicht 200 mV son- The output voltage should be 155 mV instead of La tension de sortie passe de 200 à 155 mV (voir

Page 30, chapitre 6.5.4 Niveau d'enregistrement

Page 46

Moderne Bänder können extrem hoch ausgesteuert werden. Darum wird die maximale Aussteuerung nicht mehr nach K3 definiert sondern auf 257 nWb/m bei 1000 Hz (0 VU) resp. 514 nWb/m bei 1000 Hz (0 VU + 6 dB). Die Einstellung wird über Band wie folgt vorgenommen:

- Gerät wie Bild 6.6.-74 einstellen.

Generatorpegel am Eingang so einstellen, dass der Wert am Ausgang OUTPUT 3,1 V (+ 6 dB VU) nicht überschreitet (K3 wird nicht beachtet).
Eingangspegel um 6 dB absenken und die VU-Meter auf 0 VU eichen (Trimmpotentiometer METER CALIB., Bild 6.6.–75).
Klirrfaktor über Band bei 0 VU + 6 dB darf 2 % nicht überschreiten.

Page 30, Chapter 6.6.1 Distortion Factor (via Tape), VU-meter Calibration

With modern tapes, an extremely high magnetization can be achieved. Therefore, maximum output level is not anymore determined with the distortion factor K3. 257 nWb/m by 1000 Hz corresponds to 0 VU (775 mV); 514 nWb/m by 1000 Hz corresponds to 0 VU + 6 dB (1.55 V). Calibrate via tape:

Set controls per Fig. 6.6–74.
Adjust frequency of your AF-generator according to the used bandpass filter to measure K3. Recorder's output level should not exceed 3.1 V (+ 6 dB VU). Disregard distortion K3.
Lower generator level by 6 dB and calibrate VU-meter to display 0 VU (trimmpotentiometer METER CALIB., Picture 6.6–75).
Distortion factor via tape by 0 VU + 6 dB ist not allowed to exceed 2 %.

Page 31, Chapter 6.6.2 Noise Voltage via Tape

Noise voltage measurements: refer to the 100 %

modulation (514 nWb/m)

Page 30, chapitre 6.6.1 Distorsion "après bande", étalonnage des VU-mètres

Les bandes modernes ad mettent une magnétisation beaucoup plus élevée. De ce fait le niveau maximum n'est plus défini par le taux de distorsion, mais par le niveau de référence de 257 nWb/m à 1000 Hz pour 0 VU, respectivement 514 nWb/m à 1000 Hz pour 0 VU + 6 dB. Procéder comme suit pour le réglage "après bande": FIG) URE

Placer les éléments de commande selon la fiaure 6.6-74.
Régler le générateur (fréquence selon le filtre passebande utilisé) de manière à obtenir un maximum de 3,1 V (+ 6 dB VU) sur la sortie OUTPUT. (Ne pas tenir compte de la distorsion).
Abaisser le niveau du générateur de 6 dB et régler les VU-mètres à 0 VU (potentiomètres METER CALIB., figure 6.6.—75).

Seite 31, Kapitel 6.6.2 Geräuschspannung über Band

Die Geräuschspannungsmessungen beziehen sich auf Vollaussteuerung (514 nWb/m).

Seite 32, Kapitel 6.6.4 Löschdämpfung

Der Aufnahmepegel bei 1000 Hz beträgt + 6 VU (514 nWb/m).

Page 32, Chapter 6.6.4 Erase Attenuation

The recorded reference level by 1000 Hz is + 6 VU (514 nWb/m).

Page 31, chapitre 6.6.2 Bruit de fond "après bande"

Le niveau du bruit de fond est mesuré par rapport au niveau maximum (514 nWb/m).

Page 32, chapitre 6.6.4 Profondeur d'effacement

Le niveau de référence à l'enregistrement est à + 6 dB VU (514 nWb/m).

Page 47

Page 48

Page 49

					Unspecified carbon film resistors: 1/8 W – 5 % Résistance à couche sans spécification: 1/8 W – 5 %	* * Commercial types * * Type d'usage courant
Identification Position	-	Part Name Désignation	Type / R Type / R	emarks emarques	Specifications Spécifications	Order Number Numéro de commande
	Power Supply B Plaquette alimer Connector	oard ntation connecteur	assembled	complète		1.077.540 1.077.540
0 101	Transistor	transistor	BC 177A BC 15	7 Δ		**
Q 102	Transistor	transistor	SDT 9201		TO — 5	* *
D 101	Si-Rectifier	redresseur au silicium	B 35 C 800		35 V – 800 mA	* *
D 102	Si-Rectifier	redresseur au silicium	B 40 C 2200		40 V – 2.2 A	* *
D 103	Si-Diode	diode au silicium	BA 127		50 V - 100 mA - 70°	* *
D 104	Z–Diode (Plana	r) diode Zener (planar)	ZP 12		12 V – 5% – 400 mW	* *
P 106	Trim-Potentior	neter pot. ajustable	Ruwido P 76 K		2.5 k - 0.15 W - 20 %	* *
R 101	Resistor	résistance	carbon film	à couche	1 k	* *
R 102	Resistor	résistance	carbon film	à couche	220	* *
R 103	Resistor	résistance	carbon film	à couche	820	* *
R 104	Resistor	résistance	carbon film	à couche	4.7 k	* *
R 105	Resistor	résistance	carbon film	à couche	5.6 k	* *
R 107	Resistor	résistance	carbon film	à couche	1 k – 5% – 0.3 W	* *
C 101	Capacitor	condensateur	electrolytic	électrolytique	1000 μF - 35 V	* *

C 103	Capacitor	condensateur	tantalum	au tantale	3.3 μF — 35 V	* *
C 104	Capacitor	condensateur	electrolytic	électrolytique	2500 μF - 35 V	* *
F 102	Fuse	fusible	5 x 20 mm, slo-blo	retardé	630 mA	* *
F 103	Fuse	fusible	5 x 20 mm, slo-blo	retardé	2 A	* *
					1

Page 50

	Drive Control Board	less push buttons sans touches ni		1.077.370
	Plaquette commande du mécanisme
Q 111	Transistor	BC 107 A		* *
Q 112	Transistor	BC 140 C (Siemens)		* *
D 111	Si–Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 112	Si-Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 113	Si-Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 114	S-Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 115	Si-Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 116	Si-Diode diode au silicium	BA 127	50 V - 100 mA - 70°	* *
D 117	Si-Diode diode au silicium	BA 127	50 V - 100 mA - 70 50 V - 100 mA - 70°	* *
D 110 D 119	Si-Diode diode au silicium	BA 127	50 V - 100 mA - 70 50 V - 100 mA - 70°	* *
D 120	Si-Diode diode au silicium	BA 127	50 V - 100 mA - 70°	* *
D 121	Si–Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 123	Si-Diode diode au silicium	PAB 212	50 V - 200 mA - 70°	* *
D 124	Si-Diode diode au silicium	BA 127	50 V - 100 mA - 70°	* *
D 125	Si-Diode diode au silicium	BA 127	50 V - 100 mA - 70°	* *
R 111	Resistor résistance	wire - wound bobinée	180 − 10 % − 5 W − 70°	* *
R 112	Resistor résistance	wire - wound bobinée	180 - 10 % - 5 W - 70°	* *
R 113	Resistor résistance	wire - wound bobinée	180 - 10 % - 5 W - 70°	* *
R IID	Resistor resistance	carbon film a couche	1.5 K - 10 % - 0.3 W	* *
R 117	Resistor résistance	carbon film à couche	18k-10%-03W	* *
R 118	Resistor résistance	carbon film à couche	470	* *
R 119	Resistor résistance	carbon film à couche	15 - 10 % - 0.5 W	* *
R 120	Resistor résistance	carbon film à couche	1 k	* *
R 121 - R 123	Resistor résistance	carbon comu	4.7	* *
R 125	Resistor résistance	wire - wound bobinée	1.2 K - 5 % - 9 W - 70°	* *
C 111	Capacitor condensateur	electrolytic électrolytique	500 μF — 35 V	* *
C 112	Capacitor condensateur	polyester au polyester	0.1 μF — 20 % — 100 V	* *
C 113 - C 115	Capacitor condensateur	metallized paper au papier métallisé	0.47 μF — 150 V	* *

	Delay, valeia	A v quitab contacts 120 V/c / 1 A /	12 1 190 0	56 00 0102
RELA - RELC	Relay relais	4 x switch contacts 120 v ~ / 1 A /	12 V - 180 32	56. 99.0103
	Socket socle	for relay pour relais		56, 99.0104
	Strap ressort de maintien	for relay pour relais		56. 99.0105
	Housing, Contact Slides/boîtier des curseu	s plexi plexiglas		1.077.360 - 0
	Slide, Contact curseur de contact	5 pieces		1.077.365 — 0
	Spring, Reset ressort de rappel	5 pieces		1.077.360 — 0
	Lock, spring arrêt de ressort	5 pieces		1.077.360 - 0
	Spring, Contact contact à ressort	6 pieces		1.010.001.55
			×

	Tape Drive Mécanisme	assembled complète		1.077.100
	Power Transformer assembled
	Transformateur d'alimentation complet	Т 955		1.077.525
	Voltage Selector sélecteur de tension	Philberth		53. 03.0126
	Fuse Element porte - fusible			53. 03.0113
F 101	Fuse fusible	5 x 20 mm, slo-blo retardé	220 – 250 V – 0.5 A, T	* *
F 101	Fuse fusible	5 x 20 mm, slo-blo retardé	110 – 150 V – 1 A, T	* *
C 151	Capacitor condensateur	MP (Rifa) papier métallisé	3.5 μF − 10 % − 220 V	59. 99.0451
C 152 C 153	Capacitor condensateur	MP (Rifa) papier métallisé	4.3 μF — 10 % — 220 V	59. 99.0452
C 154	Capacitor condensateur	ceramic céramique	1500 pF - 10 % - 50 V	* *
R 151 – R 154	Resistor résistance	carbon film à couche	4.7 k	* *
R 155	Photoelectric Resistor photorésistance	LDR (Philips / Valvo)		57. 99.0135
1 4 101	Leve love	2322.600.94001	0414 00 4	F4 00 04 10
LA 101	Lamp lampe	glass socket socie en verre	24 V - 30 mA	51. 02.0140
D 152	Si-Diode diode au silicium	FAB 212 RA 197	50 V - 200 mA - 70°	7 T * *
D 152		DA 127	50 V - 100 mA - 70	* *

Page 51

VU - Meter Board Plaquette des VU - mètres 1.077. 480

Color Code :

Code des couleurs :

red	=	red	rouge
org	=	orange	orange

yel	=	yellow	jaune
grn	==	green	vert
blu	-	blue	bleu
vio	=	violet	violet

brn	=	brown	brun
gry	=	gray	gris
blk	=	black	noir
wht		white	blanc

Page 52

Diag. 3

Page 53

		1/8 W – 5 % Résistance à couche sans spécification: 1/8 W – 5 %	Commercial types Type d'usage courant
Part Name Désignation	Type / Remarks Type / Remarques	Specifications Spécifications	Order Number Numéro de commande
Switch Board Plaquette commutateurs	assembled complète		1.077.435
ConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurCoding Piecepièce de codageSwitch Slidecurseur à contacts	1 piece (for / pour 1.077.700) 2 pieces (for / pour 1.077.705) 1 piece (for / pour 1.077.715) 1 piece (for / pour 1.077.710/712) 2 pieces (for / pour 1.077.720) 7 pieces		1.077.435 - 05 1.077.435 - 03 1.077.435 - 06 1.077.435 - 04 1.077.435 - 02 1.077.435 - 10 1.077.435 - 07
Circuit Board Switch, 4 / 9 Commutateur pour circuit imprimé	Playback mode switch, assembled Sélecteur du mode de reproduction complet		1.011.400
Circuit Board Switch, 3 / 10 Commutateur pour circuit imprimé	Before / After - tape switch, assembled Commutateur lecture - directe, complet		1.011.300
Circuit Board Switch, 5 / 8 Commutateur pour circuit imprimé	Input selector, assembled Sélecteur d'entrée, complet		1.011.500
Playback Cut-Off Switch Contact de coupure de la lecture	assembled complet		1.077.437
Potentiometer potentiomètre Potentiometer potentiomètre Potentiometer potentiomètre Trim-Potentiometer pot. ajustable Resistor résistance	Volume, assembled complet Balance, assembled complet Input Level, assembled complet Ruwido S 76 K carbon film à couche	250 k – 20 % – 0.15 W 560	1.077.430 - 09 1.077.430 - 08 1.077.430 - 07 * * * *
ResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceCapacitorcondensateurCapacitorcondensateurCapacitorcondensateur	carbon filmà couchecarbon filmà couchetantalumau tantaleelectrolyticélectrolytique	560 390 390 47 k 6.8 k 1 k 330 39 220 k 33 k 10 k 2.2 k 1 k 100 μF – 25 V 3.3 μF – 15 V 250 μF – 25 V
VU-Meter BoardPlaquette des VU-mètresVU-MeterVU-mètresPush-Button Switchcommuteur à toucheLamp Socketsocle de lampeSpring Contactressort de contactSpring Contactressort de contactSpring Contactressort de contactLamplampeGe-Diodediode au germaniumResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceCapacitorcondensateur	assembled complète 2 pieces Record pre-selector présélection enreg. 3 pieces 2 pieces 3 pieces AA 116 – AA 119 carbon film à couche carbon film à couche carbon film à couche carbon film à couche carbon film à couche carbon film à couche carbon film à couche carbon film à couche carbon film à couche carbon film à couche	36 V – 50 mA 100 2.7 k 2.7 k 4.7 k 3300 pF – 400 V	1.077.480 1.077.470 - 02 1.077.475 - 02 1.077.480 - 02 1.077.480 - 03 1.077.480 - 04 51. 02.0104
	Part Name DésignationSwitch BoardPlaquette commutateursConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurConnectorconnecteurContait Board Switch, 4 / 9Commutateur pour circuit impriméCircuit Board Switch, 5 / 8Commutateur pour circuit impriméPlayback Cut-Off SwitchContact de coupure de la lecturePotentiometerPotentiometerpotentiomètrePotentiometerpotentiomètrePotentiometerpotentiomètrePotentiometerpotentiomètrePotentiometerpotentiomètrePotentiometerpotentiomètreResistorrésistanceResistorResistorrésistanceResistorResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistanceResistorrésistance	Pert Name Designation Type / Remarks Type / Remarques Switch Board Plaquette commutateurs connector assembled complète Connector connectur 2 pieces (for / pour 1.077.700) Connector connectur 2 pieces (for / pour 1.077.700) Connector connectur connectur 2 pieces (for / pour 1.077.716) Connector connectur connectur connutateur pour circuit imprimé 1 piece (for / pour 1.077.720) Connutateur pour circuit imprimé Circuit Board Switch, 4 / 9 Commutateur pour circuit imprimé Selectur - directeur - directe, complet Puyback Chrolf Switch Contract de coupure de la lecture Potentiometer pot epistable Potentiometer pot epistable complet Volume, assembled complet Potentiometer pot epistable carbon film à couche carbon film à couche Resistor résistance carbon film à couche carbon film à couche Resistor résistance carbon film à couche carbon film à couche	Part Name Delignation Type / Remarks Type / Remarks Specifications Switch Board Plaquette commutatures assembled complete Specifications Connector for / pour 1077.706 } 1 piece (for / pour 1077.706 ) 2 piece (for / pour 1077.706 ) 1 piece (for / pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 1 piece (for / pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 7 pieces For pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 2 pieces (for / pour 1077.706 ) 7 pieces Connector

Page 54

Input Amplifier Amplificateur d'entrée 1.077. 700

Page 55

Input Amplifier 1.077.700 Amplificateur d'entrée

Diag. 4

Page 56

						Unspecified carbon film resistors: 1/8 W – 5 % Résistance à couche sans spécification: 1/8 W – 5 %	* * Commercial types * * Type d'usage courant
Identif Positio	ication n	F	Part Name Désignation	Type / R Type / R	lemarks Iemarques	Specifications Spécifications	Order Number Numéro de commande
		Input Amplifier	Amplificateur d'entrée	Board assembled	plaquette complète		1.077.700
Q 401	Q 421	Transistor		BC 179 B, BC 159	9 B		* *
Q 402	Q 422	Transistor		BC 109 C, BC 149	ЭС		* *
Q 403	0 423	Transistor		BC 108 B, BC 148	3 B		* *
R 401	R 421	Resistor	résistance	carbon film	à couche	1 M	* *
R 402	R 422	Resistor	résistance	carbon film	à couche	180 k	* *
R 403	R 423	Resistor	résistance	carbon film	à couche	100 k	* *
R 404	R 424	Resistor	résistance	carbon film	à couche	22 k	* *
R 405	R 425	Resistor	résistance	carbon film	à couche	47	* *
R 406	R 426	Resistor	résistance	carbon film	à couche	100 k	* *
R 407	R 427	Resistor	résistance	carbon film	à couche	18 k	* *
R 408	R 428	Resistor	résistance	carbon film	à couche	6.8 k	* *
R 409	R 429	Resistor	résistance	carbon film	à couche	33 k	* *
R 410	R 430	Resistor	résistance	carbon film	à couche	6.8 k	* *
R 411	R 431	Resistor	résistance	carbon film	à couche	220	* *
R 412	R 432	Resistor	résistance	carbon film	à couche	68 k	* *
C 401	C 421	Capacitor	condensateur	tantalum	au tantale	10 μF — 15 V	* *
C 402	C 422	Capacitor	condensateur	tantalum	au tantale	3.3 μF — 15 V	* *
C 403	C 423	Capacitor	condensateur	ceramic	céramique	1500 pF - 10 % - 50 V	* *
C 404	C 424	Capacitor	condensateur	electrolytic	électrolytique	125 μF — 3 V	* *
C 405	C 425	Capacitor	condensateur	electrolytic	électrolytique	50 µF — 3 V	* *
C 406	C 426	Capacitor	condensateur	ceramic	céramique	22 pF - 10 % - 50 V	* *
C 407	C 427	Capacitor	condensateur	tantalum	au tantale	10 μF — 15 V	* *
		l		I

Page 57

Frequency Characteristic, Record Amplifier 3 3/4 ips Courbe de réponse de l'ampli d'enregistrement à 3 3/4 in/s Test Set-up as above Dispositif de mesure comme ci-dessus

Page 58

Record Amplifier Amplificateur d´enregistrement 1.077.705

Diag. 5

Page 59

					Unspecified carbon film resistors: 1/8 W - 5 % Résistance à couche sans spécification : 1/8 W - 5 %	* * Commercial types * * Type d'usage courant
dentification Position	Pa Di	rt Name ésignation	Туре / Туре /	Remarks Remarques	Specifications Spécifications	Order Number Numéro de commano

	Record Amplifier Amplificateur d'e	enregistrement	Board assembled	plaquette complète		1.077.705
501	Transistor		BC 109 B, BC 149	9 B		* *
502	Transistor		BC 108 B, BC 148	3 B		* *
503	Transistor		BC 178 A, BC 15	ВА		* *
0.504 Q.505	Transistor		BC 108 B, BC 148	3 B		* *
501 P 502	Trim-Potentiome	ter pot. ajustable	Ruwido P 76 K		20 k - 10 % - 0.15 W	* *
503	Trim-Potentiome	ter pot. ajustable	Ruwido P 76 K		20 k - 20 % - 0.15 W	* *
504	Trim-Potentiome	ter pot. ajustable	Ruwido P 76 K		500 - 20 % - 0.15 W	* *
501 R 502	Resistor	résistance	carbon film	à couche	100 k	* *
503	Resistor	résistance	carbon film	à couche	1.5 k	* *
504	Resistor	résistance	carbon film	à couche	3.3 k	* *
505	Resistor	résistance	carbon film	à couche	3.9 k	* *
506	Resistor	résistance	carbon film	à couche	1 k	* *
507	Resistor	résistance	carbon film	à couche	1 k	* *
508	Resistor	résistance	carbon film	à couche	56 k	* *
509	Resistor	résistance	carbon film	à couche	1.8 k	* *
510	Resistor	résistance	carbon film	à couche	4.7 k	* *
511 R 513	Resistor	résistance	carbon film	à couche	220 k	* *
512	Resistor	résistance	carbon film	à couche	56 k	* *
514	Resistor	résistance	carbon film	à couche	100 k	* *
515	Resistor	résistance	carbon film	à couche	330	* *
516	Resistor	résistance	carbon film	à couche	1 k	* *
517	Resistor	resistance	carbon film	a couche	680	**
518	Resistor	résistance	carbon film	à couche	2.2 k	* *
501 C 510	Capacitor	condensateur	tantalum	au tantale	3.3 μF — 15 V	* *
502	Capacitor	condensateur	electrolytic	électrolytique	100 μF — 3 V	* *
503	Capacitor	condensateur	ceramic	céramique	47 pF - 10 % - 50 V	* *
504	Capacitor	condensateur	polyester	au polyester	0.1 μF — 10 % — 100 V
505	Capacitor	condensateur	polyester	au polyester	3300 pF - 10 % - 400 V	**
506	Capacitor	condensateur	polyester	au polyester	2700 pF - 10 % - 400 V	**
507	Capacitor	condensateur	electrolytic	électrolytique	25 μF — 25 V	**
508	Capacitor	condensateur	polystyrene	au polystyrene	180 pF - 10 % - 160 V
509	Capacitor	condensateur	electrolytic	electrolytique	10 µF - 35 V
511	Capacitor	condensateur	tantalum	au tantale	1μF - 15 V	**
512	Capacitor	condensateur	nolvestor		4/μr - 3 V	* *
513	Capacitor	condensateur	polyester	au polyester	0.033 µF - 10 % - 250 V	**
514	Capacitor	condensateur	tontolum	au polyester	0.01 μF - 10 % - 160 V	**
516	Capacitor	condensateur	nolvestor		3.3 $\mu$ F - 30 V	**
510	Capacitor	condensateur	poryester	au polyester	3300 pr - 10 % - 400 V	**
51/	Capacitor Chalks Oall	condensateur	polystyrene	au polystyrene	390 pF – 5 % – 160 V	1 077 750
501	Choke Coll	bobine d'arret	assembled	complete		1.077.750
502	Choke Coll MPX	DODINE G'arret MPX	assembled	compléte		1.077.707

Page 60

Oscillator Oscillateur 1.077.712

Page 61

Test points Points de mesure	2 - Track 2 - pistes	4 - Track 4 pistes
A	approx. 22V/120 kHz	approx. 18V/120 kHz
В	approx. 44V/120 kHz	approx. 36V/120 kHz
© + D	500 mV/120 kHz 50 mV/ 1 kHz*	400 mV/120 kHz 40 mV/ 1 kHz*

OSCILLATOR COIL L 70	3	PCB
1.022.110 (older version) 1.077.760	no indication red point on surface	1.077.710 1.077.712

OSCILLATOR COIL L 70	4	РСВ

Test values (C) and (D) depend on type and speed of tape; they are to be considered

Les tensions aux points (C) et (D) diffèrent suivant le type et la vitesse de la bande; les valeurs

Oscillator 1.077.712 Oscillateur

Diag. 6a

Page 62

					Unspecified carbon film resistors: 1/8 W – 5 % Résistances à couche sans spécification: 1/8 W – 5 %	Commercial types Type d'usage courant
Identification Position	Identification Part Name Position Désignation		Type/Re Type/Re	marks marques	Specifications Spécifications	Order Number Numéro de commande
	Oscillator Board	Plaquette oscillateur	2-track, assembled	2 pistes, complète	red dot on oscillator coil point rouge sur bobin. oscill.	1.077.712
			4-track, assembled	4 pistes, complète	yellow dot on oscillator coil point jaune sur bobin. oscill.	1.077.731
Q 703 – Q 704	Transistor		BC 140 - 10			**
R 715	Resistor	résistance	carbon film	à couche	18 k	**
R 716 – R 719	Resistor	résistance	carbon film	à couche	1 k	**
R 720 – R 723	Trim-potentiometer	pot. ajustable	carbon type	au carbone	50 k – 20 % – 0,15 W	**
C 708	Capacitor	condensateur	polystyrol	au polystyrol	470 pF — 5 % — 160 V	* *
C 709	Capacitor	condensateur	polystyrene	au polystyrène	3,3 nF — 1 % — 125 V	* *
C 710 – C 711	Capacitor	condensateur	polystyrol	au polystyrol	220 pF — 5 % — 160 V	**
C 712	Capacitor	condensateur	electrolytic	électrolytique	250 µF — 25 V	**
L 703	Oscillator coil	bobinage oscillateur	2-track, assembled	2 pistes, complète		1.022.110
L 704	Oscillator coil	bobinage oscillateur	4-track, assembled	4 pistes, complète		1.022.112
L 705	Choke coil	bobine d'arrêt	assembled	complète		1.077.707

Page 63

Record Relay Relais d'enregistrement 1.077. 715

Page 64

Record Relay Relais d'enregistrement

Diag. 7

Page 65

					Unspecified carbon film resistors: 1/8 W – 5 % Résistance à couche sans soécification: 1/8 W – 5 %	* * Commercial types * * Type d'usage courant
Identification Position	Pa Di	rt Name ésignation	Туре / F Туре / F	Remarks Remarques	Specifications Spécifications	Order Number Numéro de commande
Q 601 D 601 R 601 R 602 R 603 R 604 C 601 C 602 REL 601 L 601	Record Relay Transistor Si-Diode Resistor Resistor Resistor Resistor Capacitor Capacitor Relay Dummy Head	Relais d'enregistrement diode au silicium résistance résistance résistance résistance condensateur condensateur relais bobine de charge fictive	Board assembled AC 128, AC 152 BA 127 carbon film carbon film carbon film carbon film polyester electrolytic ITT PZ 4/A 2 610 assembled complè	plaquette complète á couche à couche à couche à couche au polyester électrolytique ( 24 ) te	50 V – 100 mA 10 1 k 3.3 k – 10 % – 0,3 W approx. 1.2 k – 0.5 W 0.47 μF – 20 % ~ 100 V 500 μF – 3 V	1.077.715 56. 04.0121 1.077.755

Page 66

Playback and Drive Amplifier Amplificateurs de lecture et de ligne 1.077. 720

Frequency Characteristic, Playback Amplifier (current driven) Courbe de réponse de l'ampli de lecture (générateur à courant constant)

Page 67

Diag. 8

Page 68

					1/8 W - 5 %
dentification Position		Part Name Désignation		Remarks Remarques	Specifications Spécifications	Order Number Numéro de command
	Playback Amp Amplificateur	blifier de reproduction	Board assembled	plaquette complète		1.077.720
	Transistor		BC 109 C BC 149	9.0		* *
0 803	Transistor		BC 109 B, BC 149	9 B		* *
2 804 Q 805	Transistor		BC 108 B, BC 14	8 B		* *
R 801	Resistor	résistance	carbon film	à couche	220 k	* *
R 802 R 803	Resistor	résistance	carbon film	à couche	100 k	* *
R 804	Resistor	résistance	carbon film	à couche	220	* *
R 805	Resistor	résistance	carbon film	à couche	12 k	* *
R 806	Resistor	résistance	carbon film	à couche	68	* *
R 807	Resistor	résistance	carbon film	à couche	1 4	* *
R 808	Resistor	résistance	carbon film	à couche	330 k	* *
R 809 R 811	Resistor	résistance	carbon film	à couche	4.7 k	* *
R 810	Resistor	résistance	carbon film	à couche	2.2 k	* *
R 813	Resistor	résistance	carbon film	à couche	1.6	* *
R 814	Resistor	résistance	carbon film	à couche	330	* *
R 815	Resistor	résistance	carbon film	à couche	150 k	* *
R 816	Resistor	résistance	carbon film	à couche	150 k	* *
R 817	Resistor	résistance	carbon film	à couche	330	* *
R 818	Resistor	résistance	carbon film	à couche	10 k	* *
R 819	Resistor	résistance	carbon film	à couche	68	* *
R 820	Resistor	résistance	carbon film	à couche	1 k	* *
R 821	Resistor	résistance	carbon film	à couche	1 k	**
R 822	Resistor	résistance	carbon film	à couche	22 k	* *
° 801	Trim-Potentio	meter pot. ajustable	Ruwido P 76 K		20 k - 20 % - 0.15 W	* *
C 801	Capacitor	condensateur	Polystyrol	au polystyrol	330 pF - 5 % - 160 V	* *
C 802	Capacitor	condensateur	tantalum	au tantale	3.3 µF - 15 V	* *
C 803	Capacitor	condensateur	electrolytic	électrolytique	1600 μF – 3 V	* *
C 804	Capacitor	condensateur	electrolytic	électrolytique	3.3 µF - 35 V	* *
C 805	Capacitor	condensateur	polyester	au polyester	.01 μF - 5 % - 160 V	* *
C 806 C 812	Capacitor	condensateur	polystyrene	au polystyrène	100 pF - 10 % - 160 V	* *
C 807	Capacitor	condensateur	polyester	au polyester	1000 pF - 10 % - 400 V	* *
C 808	Capacitor	condensateur	polystyrene	au polystyrène	390 pF - 5 % - 160 V	* *
C 809	Capacitor	condensateur	polyester	au polyester	3300 pF - 10 % - 400 V	* *
C 810	Capacitor	condensateur	tantalum	au tantale	3.3 μF — 15 V	* *
C 811	Capacitor	condensateur	electrolytic	électrolytique	100 µ́F – 3 V	* *
C 813	Capacitor	condensateur	electrolytic	électrolytique	25 μF – 25 V	* *
	Capacitor	condensateur	tantalum	au tantale	10 μF – 15 V	* *
C 814

Unspecified carbon film resistors :

Page 69

Loudspeaker Amplifier Amplificateur de haut-parleur

Page 70

Loudspeaker Amplifier Amplificateur de haut-parleur

Diag. 9

Page 71

					1/8 W - 5%	* * Commercial types * * Type d'usage courant
Identification Position	Pa	art Name ésignation .	Type / Type /	Remarks Remarques	Specifications Spécifications	Order Number Numéro de command
Q 901	Loudspeaker An Amplificateur d Transistor	mplifier le haut-parleur	Board assembled BC 177 A, BC 15	plaquette complète		1.077.850
Q 901	Transistor		BC 107 A/B, BC	147 A/B		* *
Q 903	Transistor		BC 107 A/B			**
0 904	Transistor		BC 177 A	`
0.905 0.906	l ransistor	at a da su stitut su	BD 121 (Philips	)	F0.1/ 100 m 0
D 901 D 902	SI-Diode Si Rootifior	diode au silicium	BA 127 B 40 C 2200		50 V - 100 mA	**
B 901 - B 903	Besistor	résistance	carbon film	à couche	47 k	* *
R 904	Resistor	résistance	carbon film	à couche	3.3 k	* *
R 905	Resistor	résistance	carbon film	à couche	2.2 k	* *
R 906	Resistor	résistance	carbon film	à couche	680	* *
R 907	Resistor	résistance	carbon film	à couche	3,3 k	* *
R 908	Resistor	résistance	carbon film	à couche	1 k	* *
R 909	Resistor	résistance	carbon film	à couche	6.8 k	* *
R 910	Resistor	résistance	carbon film	à couche	680	* *
R 911	Resistor	résistance	carbon film	à couche	220	* *
R 912 R 920	Resistor	résistance	carbon film	à couche	680	* *
R 913	Resistor	résistance	carbon film	à couche	3.3 k	**
R 914 R 915	Resistor	résistance	carbon film	à couche	47	* *
R 916 R 917	Resistor	résistance	wire	bobinée	1 – 10 % – 1 W
R 918 R 919	Resistor Resistor	résistance résistance	carbon film carbon film	à couche à couche	3.3 k 4.7 k	* *
C 901	Capacitor	condensateur	tantalum	au tantale	4.7 µF - 10 V
C 902	Capacitor	condensateur	tantalum	au tantale	47 µF - 3 V	**
C 903	Capacitor	condensateur	ceramic	céramique	220 pF - 10 % - 50 V	**
C 904	Capacitor	condensateur	tantalum	au tantale	10 µF - 15 V	**
C 905 C 906	Capacitor	condensateur	polyester	au polyester	0.1 μF - 20 % - 100 V	**
C 907 C 908	Capacitor	condensateur	electrolytic	électrolytique	2500 μF – 25 V	**
C 909	Capacitor	condensateur	polyester	au polyester	.1 μF — 20 % — 100 V	**
F 901	Fuse	fusible	5 x 20 slo-blo	retardé	1.25 A	**
	Additional for final transistor	amplifier with SDT 9201 s
	Variante avec t	ransistors de puissance SDT 92
0.905 0.906	Transistor		SDT 9201	- énominue	500 - 5 40 M 50 M	**
0 910	Capacitor	condensateur	ceramic	ceramique	500 pr - 10 % - 50 V	**
C 911	Capacitor	condensateur	bridged	ceramique	4/ pr - 10 % - 50 V	10 x 10
n 914 P 015	Resistor	resistance	bridged	court-circuitée
1 913	Resistor	10313LdHUC	bridged	Sourcemented

Page 72

Page 73

Diag. 10

Page 74

	Pos.	Bauteil No.		Bezeichnung				Stk.	Bemerkung
	C 201	59.31.4473		C 47N	20%	160V	MPETP
	202	59.31.4104		c .lu,	20%	160V	MPETP
	203	59.22.8100	0	2 100;	100%	63V	EL	1
	204	59.32.3472		24,7N,	100%	40V	KER
	205	59.32.3472	0	C 4,7N,	100%	40V	KER
	206	59.32.3472		24,7N,	100%	40V	KER
	207	59.32.3472	0	C 4,7N	100%	40V	KER
	208	59.31.4104		.lu	2.0%	160V	MPETP
2	209	59.12.8162	(	2 1.6N,	1%	125V	PS
	210	59.11.4472	0	24,7N	2,5%	160V	PC
	211	59.31.4103		lon,	20%	160V	PETP
	212	59.22.4470		247U,	100%	16V	EL
	213	59.22.8100		2 100	100%	63V	EL
	214	59.22.8100		. 10U,	100%	63V	EL
	215	59.30.6109		: lu,	50%	35V	TA
	216	59.31.4103	C	: 10N,	20%	160V	PETP
	217	59.31.1224		.220,	.20%	100V	MPETP
	218	59.30.4100	0	: 100,	50%	16V	ТА
	219	59.30.6109	0	: 10,	50%	16V	ТА
	220	59.99.0450		.470,	20%	150V	MP
	221	59.22.6470	C	47U,	50%	40V	EL


	D 201	50.04.0125	I	1N4448			SI
	202	50.04.0125
	203	50.04.0125	I
	204	50.04.0125	E
	205	50.04.0125	E
	206	50.04.0125	E				***
	207	50.04.0125	D
	208	70.01.0223	D	BY 15	9 / 400	)	SI
(3)	209	50.04. 1122	L	) 18V	5%	4W	ST
	TC 201	FO OF 0227
9	202	50.05.0257		C SN 761	31 N		LIN
	Aenderung	en 6 16 6 7	70			211718	TIMER	71 8	QUE 1 212
			ongliste					2.16 MM	1. 375.4. Tr Kum.
	SIUUE	H POSITIC	ns	iste		Consider 7 Rom.			. 74 Rom.
	ZURICH	RF Regelpi	int	9,5 / 3	L9		Blatt	1	Blätter: 2
	Kopie für: Ersatz für:							amenoine duone T	Didiler. 3
	Ersetzt durch:							1.077	.724

Page 75

	CONTRACTOR DATA AND ADDRESS OF AD	CODE COMPANY	CONCORT & REQUIREMENTS	COMPANY OF THE OWNER	wyth address of the state			Concession and the	All PERSONNAL PROPERTY.		THE R. LEWIS CO., LANSING MICH.
	Pos.	Ba	uteil No		Bez	eichn	ung					Stk.	Bemerkun	g


	Q 201	50	.03.04	38	Q	В	c 10	8 B a	equi	v.	NPN
	202	50	03.04	38	Q
	203	50	.03.04	38	Q
	204	50	.03.03	18	Q	B	C 17	8 B a	equi	v.	PNP
1	205	50	.03.04	77	Q	R	CA 4	.11			NPN


	R 201	57	41.41	03	R	10	K,	5%,		.25w,	CSCH
	202	57	.41.41	03	R	10	к,
	203	57	.41.41	03		10	к,
5	204	57	41.41	22		1	к,
	205	57	41.43	32		3,3	к,
	206	57	41.42	23		22	к,
	207	57	41,42	23		22	к,
	208	57	41.42	23		22	К,
	209	57	41.42	23		22	к,
	210	57	41.43	32		3,3	K,
	211	57.	41.41	03		10	к,
	212	57.	41.41	03		10	K,
	213	57.	41.44	72		4,7	к,
	214	57	41.42	23		22	K,
	215	57	41.41	03		10	K,
	216	57.	41.42	23		22	к,
	217	58.	.99.01	26	R	10	к,	20%,	T-S	chicht	PCSCH	1
	218	57	99.01	79	R 8	6,6	к,	1%	50	PPm	MF
	219	57.	41.48	21	R	820	,	5%		.25W	CSCH
	220	57.	41.42	21		220	,
01000	221	57.	41,44	72		4,7	К,
	222	57.	41.42	22		2,2	К,
1000	223	57.	41.42	22		2,2	к,
	224	57.	41.41	05		1	М,
	225	57.	41.46	82		6,8	к,
-	226	57.	41.43	30		33	,
Community of Community	Aenderung	jen	6 16.6	. 77 . 14	2m. 0		the constant Las	3	24.6	76 Ra	4	harris and the second	5 5.4	. 22 Jac
	STUDE	R	Posi	tions	slist	е					Erstell	t: 27.5	.74 Rom
	REGENSDO	ORF				-					Geprüf	t:	Rom
-	ZURICH	1	Rege	lprin	t	9,5	/ 19	9			Blatt:	2	Blätter	3
and a local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion of the local diversion	Kopie für:			Ersat	z für:
	2010/00/00/00/00/00/00/00/00/00/00/00/00/	-		Erset	zt dur	ch:	NOTION AND	NINCOLLING	-		1	077.	724

Pos.	Bauteil N	0.	Bezeichr	nung				Stk.	Bemerkur	ıg
R 227	57.41.4	472	R 4,7	κ,	5%	.25W	CSCH
228	57.41.4	102	3	к,
229	57.41.4	152	1,5	к,
230	57.41.4	222	2,2	к,
231	57.43.4	100	10	),		.5W
232	57.41.4	683	68	в к,		.25W
233	57.41.4	473	47	к,
234	57.41.4	473	47	К,
235	57-41-4	220	2	2,




















Aenderung	en 6 16,	6.77 Rom	- (F)		3:	24.6.76 Ro	. 46.	12. 16.1	. 5.15.4	Him.
STUDE	R Pos	itions	liste				Erstell	t: 27.5	.74 Ron	ι.
REGENSDO	RF	elprin	t 9,5	/ 19			Geprüf	t:	Pom.	2
Kopie für:		Ersatz	für:				Diait:	ن	BIGITER	S
	Erset		t durch:				1.077.724

Page 76

11. REPLACEMENT PARTS LIST

The replacement parts list is divided into following columns :

INDEX	The index number matches the one on the illustration Take note of the letters referring to said illustration.
QUANTITY ( QTY )	Indicates the number of parts in the assembly.
PART NAME	The short designation, obligatory, is to be included when writing orders.
	Use these part numbers only on all orders.

Note : All Orders Must be with Order Number and PART NAME.

In - production changes are noted on separate sheets (e.g. PL 6a). Red index numbers designate these separate sheets.

Check the separate sheets when ordering, please.

Page 77

ΩΤΥ	PART NAME	ORDER NUMBER
1	Carrying case, assembled	1.077.831
1	Cover, case, assembled	1.077.834
1	Side, left, with loudspeaker	1.077.832
1	Side, right, with loudspeaker	1.077.833
4	Loudspeakers	71. 01.0102
	Loudspeakers From No 277664	71. 01.0150
	Loudspeakers From No 279969	71. 01.0151

1	Handle, carrying, assembled	1.077.805
1	Fastener, handle	1.077.800 - 08
1	Cover, voltage selector, with frame	1.077.806
1	Cover, plastic " connections "	1.077.800 - 01
1	Cover, plastic " air access "	1.077.800 - 06
4	Support, rubber, case fastening	1.077.800 - 20

	Lock
1	Case lock	33. 01.0104

1	Кеу	33. 01.0106

	Fastenings, carrying case
4	Screw, sheet metal	20. 21.7311
4	Washer	23. 01.3043
4	Foot, case	1.077.831 - 02

1	Cabinet, walnut, assembled	1.077.800

	Feet, for vertical operation
2	Rail, plastic, less feet	1.077.800 - 03
4	Foot, rubber	1.077.800 - 04

	Fastenings, walnut cabinet
4	Screw, sheet metal	20. 21.7310
4	Washer	1.010.007 - 23

1	Disconnector, protectiv	1.077.845
1	Installation unit, sheet metal incl. fasteners	1.077.840
3	Fastener	1.040.255
4	Screw, sheet metal	20. 21.7308

Page 78

INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
Δ		Chaseis
01	1	Chassis tape drive	1.077.100 - 01
02		Frame, left	1.077.100 - 02
03	1	Frame, right	1.077.100 - 03
04	1	Chassis, switch board	1.077.430 - 01
05	1	Panel, shield	1.077.114
06	1	Rail, terminal	1.077.550
07	16	Snapnut	22. 16.2021
08	4	Screw, sheet metal	20. 21.7312
09	4	Washer	1.010.008 - 23
10	8	Screw, sheet metal	20. 21.7308
11	2	Bracket, double angle	1.077.100 - 18

		Plastic Cover, Knobs
	1	Cover, drive	1.077.600
		Cover, drive, for MK II, III, IV	1.077.650
		Panel, front, VU - port bridged	1.077.604
		Panel, front, for MK III	1.077.652
		Panel, front, for MK IV	1.077.670
	1	Lid, assembled	1.077.609
		Lid, for MK III	1.077.660
		Lid, for MK IV	1.077.661
	2	Spring, lid	1.077.603 - 01
	1	Cover, head	1.077.665
	4	Knob, rotary, gray MK III	1.077.632
		Knob, rotary, gray MK IV	1.077.631

	1	Knob, rotary, balance	1.077.633
	4	Skirt, knob, clear	1.077.625 - 01
		Skirt, knob, for MK III	1.077.626 - 01
		Skirt, knob, Tape - Input	1.077.644
		Skirt, knob, Stereo - I - II - Mono	1.077.645

		Skirt, knob, NAB -Input - IEC	1.077.646
		Skirt, knob, CH 1	1.077.647
		Skirt, knob, CH 2	1.077.648
		Kooh quitch POWER for MK III	1.077.636
	1	Knob switch POWER for MK IV	1.077.637
		KIUD, SWILLI, FOWER, IDE WIK TY

10.72

Page 79

INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
в		Push Button, Unit
01	1	Bearing strip, push button (incl. 5 bars)
02	5	Bracket, plastic ( clear )	1.077.490 - 04
03	4	Push button, gray	1.077.490 - 05
04	1	Push button, red	1.077.490 - 06
05	1	Shield plate	1.077.100 - 14
06	1	Spring, tension, tape lift	1.077.100 - 11
07	1	Bar switch, " Speakers Off " " Reel Motors Off ", assembled	1.077.355 - 03
		Socket
08	3	Socket, Jack, assembled	1.077.500
09	2	Shield plate	1.077.430 - 06
		VU - Meter
10	2	VU-Meter	1.077.470 - 03
		VU-Meter for MK III	1.077.470 - 04
11	1	Bracket	1.077.485
12	1	Support	1.077.470 - 01
13	2	Push button, red	1.077.475 - 01
14	2	Switch, slide,	1.077.475 - 03
	1	Lamp socket for MK III	1.077.471
15	7	Socket, plug, assembled	1.077.115
16	7	Sleeve, spring	1.077.100 - 21
		Switch, Boałd
17	1	Housing, switch ( Before / after tape switch )	1.011.300 - 01
17	1	Housing, switch ( Playback mode switch )	1.011.400 - 01
17	2	Housing, switch ( Input selector )	1.011.500 - 01
18	4	Rotor, incl. hollow shaft	1.011.180
19	4	Spring, compression ( indexing )	1.011.200 - 04
20	4	Ball (indexing)	41. 01.0130
21	13	Contact	1.010.001 - 55

10.72

Page 80

INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
С		Switch, Power
01	1	Switch, power, assembled	1.077.440
02	1	Micro-switch (tape tension)	55. 01.0124
03	2	Rivet, tubular	28. 21.1415
04	2	Micro-switch ( line )	55. 01.0124
05	4	Bushing, insulation	1.077.440 - 08
06	1	Foil, insulation	1.077.440 - 05
07	2	Spring, flat	1.077.440 - 03
08	1	Ball	41. 01.0160
09	2	Bearing, plastic	1.077.450 - 04
10	4	Clip, retaining Ø 4 mm	24. 16.3040
11	1	Cam, switch (white plastic) with bushing	1.077.450
12	1	Lever	1.077.460
13	1	Bearing	1.077.455
14	2	Ring, retaining Ø 2.3 mm	24. 16.3023
15	1	Washer, tap, hard paper	1.077.440 - 04
16	1	Stop ( turn limiting )	1.077.445 - 02
17	1	Bar	1.077.430 - 04
18	1	Link, connecting	1.077.430 - 03
01 02 03 04 05 06 07 08	1 1 3 2 1 1 1	Rail, Connector Rail, connector, with power cable and remote control cabling Enclosure, protective disconnector Socket, instrument Socket, twin, Cinch Socket, loudspeaker Socket, 5 - pole RADIO Socket, 10 - pole, REMOTE CONTROL Plug, dummy, remote control, assembled	1.077.550 1.077.555 54.04.0103 54.02.0293 54.02.0301 54.02.0310 54.02.0315 1.077.570

Page 81

INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
E		Drive, Tape & Headblock
01	1	Chassis, cast, tape drive, with pressure lever sintered bearings
02	4	Cup, tape guide	1.736.222 - 04
03	2	Collar, tape auide	1.736.222 - 05
04	2	Bushing, threaded	1.077.120 - 02
05	4	Screw M 4 x8	21. 01.0455
06	1	Post, tape guide	1.077.120 - 01
07	2	Screw M 3 x 8	21. 01.0355
08	1	Guide, tape, assembled	1.077.145
09	1	Bracket, assembly	1.077.150
10	1	Spring, compression	1.077.145 - 03
11	2	Disc , guide	1.077.145 - 01
12	1	Sleeve, spacer	1.077.145 - 02
13	1	Nut, hex M 3	22. 01.5030
14	1	Lever, tape lift, assembled	1.077.175
15	1	Screw , spec	1.077.120 - 03
16	1	Washer	1.077.120 - 04
17	1	Bracket	1.077.133
18	1	Socket, lamp	53. 04.0102
19	1	Lamp ( 24 V, 30 mA ),	51. 02.0140
20	1	Resistor, photoelectric ( end-of-tape switch )	1.077.135
21	1	Base plate, assembled (2 - hole head-fastening)
22	1	Base plate, assembled (1 - hole head-fastening)	1.077.157
23	2	Housing, shield, ext (2 - hole head-fastening)
24	2	Housing, shield, ext (1 - hole head-fastening)	1.077.155 - 05
25	2	Housing, shield, int (2 - hole head-fastening)
26	2	Housing, shield, int (1 - hole head-fastening)	1.077.155 - 06
	4	Plastic pin	1.077.155 07
27	1	Lid, shield, playback head, assembled	1.077.165
28	1	Head, playback, 2 - track, ( 2 - hole head-fastening )	1.116.026
	1	Head, playback, 4 - track, ( 2 - hole head-fastening )	1.116.046
29	1	Head, playback, 2 - track, (1 - hole head-fastening)	1.116.027
	1	Head, playback, 4 - track, ( 1 - hole head-fastening )	1.116.047
30	1	Head, record, 2 - track, (2 - hole head-fastening)	1.116.021
	1	Head, record, 4 - track, (2 - hole head-fastening)	1.116.041
31	1	Head, record, 2 - track, (1 - hole head-fastening)	1.116.022
	1	Head, record, 4 - track, (1 - hole head-fastening)	1.116.042
32	1	Head, erase, 2 - track	89. 01.0301
	1	Head, erase, 4 - track	89. 01.0302
33	1	Shim, 4 - track head	1.077.131 - 01
	1	0.1 mm shim, brass for elevation adjustment of erase head	1.010.006 - 23

Page 82

INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
E			×
34	1	Screw, spec (erase head fastening)	1.077.130 - 02
35	4	Screw, spec (Rec / Play head fastening, 2 - hole)	21. 99.0114
36	2	Screw, spec ( Rec / Play head fastening, 1 - hole )	21. 99.0118
37	4/2	Washer, head fastening	23. 01.1032
38	4/2	Washer, securing, head fastening	24. 16.1030
39	2	Screw M 2 x 3, screen lid	21. 01.0201
40	7	Screw M 3 x 6	21. 01.0354
41	4	Setscrew M 3 x 6	21. 18.6354

12	1	lower program according with pressure reller	1 077 205
42	1		1.077.305
43	1		1.077.312
44			1.077.305 - 05
45	2	washer, tenon	1.736.200 - 04
40		Snap	1.736.200 - 03
4/		Lever, pressure, stripped	1.077.305 - 02
48		Lever	1.077.305 - 01
49	2	Setscrew, spec	1.077.305 - 06
50	1	Screw, hex head, M 4 x 14	1.077.305 - 07
51	1	Spring, compression	1.077.305 - 04
52	2	Washer, hard paper
53	1	Shaft	1.077.305 - 03
54	1	Lever	1.077.320
55	1	Link	1.077.100 - 10
56	2	Clip Ø 3.2 mm	24. 16.3032
57	1	Lever	1.077.325
58	2	Setscrew, spec	1.077.325 - 03
59	1	Clevis	1.077.330 - 01
60	1	Screw M 3 x 6	21. 01.0354
61	1	Washer, lock	24. 16.1030
62	1	Plunger	1.077.330
63	1	Solenoid, assembled	1.014.700*
64	1	Nut, hex M 4	22. 01.8040
65	1	Washer	23. 01.3043
66	1	Lever, trip, with knob	1.077.340
67	1	Knob, trip lever	1.736.790 - 02
68	1	Spring, helical	1.077.100 - 08
69	2	Bolt	1.077.100 - 07
70	2	Bolt, threaded	1.736.375 - 01
71	1	Washer	1.736.502 - 04

Page 83

Page 84

E 1 reeler 01 1 Chassis, cast, tape drive, with pressure lever sintered bearings 1.077.126 02 2 Sleeve, threaded 1.077.121 - 01 03 2 Nut, hex 22.99.0103 04 4 Cap, guiding 1.077.121 - 02 05 2 Washer 1.077.121 - 02 06 2 Washer 1.077.121 - 02 06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121 - 05 08 1 Stud, threaded 1.077.121 - 05 08 1 Stud, threaded 1.077.121 - 05 11 1 Bott, guiding 1.077.121 - 05 12 1 Screw, machine, slotted head M 3 x 6 2.01.0354 13 1 Screw, machine, slotted head M 3 x 6 2.01.0354 13 1 Screw, complet 1.077.310 14 1 Washer 1.077.331 - 02 15 1 Brom S 37/51 + G 43228 1.077.331 - 02<	INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
01 1 Chassis, cast, tape drive, with pressure lever sintered bearings 1.077.126 02 2 Sleeve, threaded 1.077.121 - 01 03 2 Nut, hex 22.99.0103 04 4 Cap, guiding 1.077.121 - 02 05 2 Washer 1.077.121 - 02 05 2 Washer 1.077.121 - 02 06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121 - 05 08 1 Ring, plain 1.077.121 - 04 09 1 Stud, threaded 1.077.121 - 06 10 1 Feeler, assembled 1.077.121 - 06 11 1 Bolt, guiding 1.077.185 12 1 Screw, machine, slotted head M 3 x 6 21.01.0364 13 1 Spring, tension 1.077.121 - 07 14 1 Washer 1.077.121 - 07 15 1 Bracket (angle), with spring 1.077.31 16 1 Nut,	Е1		Feeler
02 2 Sleeve, threaded 1.077.121 - 01 03 2 Nut, hex 22.99.0103 04 4 Cap, guiding 1.077.121 - 02 05 2 Washer 1.077.121 - 02 06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121 - 05 08 1 Ring, plain 1.077.121 - 04 09 1 Stud, threaded 1.077.121 - 04 09 1 Screw, shoulder 1.077.121 - 04 1007.121 1 Bolt, guiding 1.077.121 - 04 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121 - 07 14 1 Washer 1.077.121 - 07 15 1 Bracket (angle), with spring 1.077.121 - 07 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331 - 02 10 1 Screw, hex, head dog point 1.077.	01	1	Chassis, cast, tape drive, with pressure lever sintered bearings	1.077.126
03 2 Nut, hex 22.99.0103 04 4 Cap, guiding 1.077.121 - 02 05 2 Washer 1.077.121 - 02 05 2 Washer 1.077.121 - 02 05 2 Washer 1.077.121 - 02 05 2 Swasher 1.077.121 - 01 06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121 - 05 08 1 Ring, plain 1.077.121 - 04 09 1 Stud, threaded 1.077.121 - 06 10 1 Feeler, assembled 1.077.185 11 Bolt, guiding 1 1.077.121 - 07 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121 - 07 14 1 Washer 1.077.310 15 1 Bracket (angle), with spring 1.077.330 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 - 02 18 1 Screw, collared 1.077.331 - 02 19 1 Screw, hex, head dog point 1.077.305 - 03 10 Shaft	02	2	Sleeve, threaded	1.077.121 - 01
04 4 Cap, guiding 1.077.121 - 02 05 2 Washer 1.077.121 - 09 05 2 Washer 1.077.121 - 09 06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121 - 05 08 1 Ring, plain 1.077.121 - 04 09 1 Stud, threaded 1.077.121 - 06 10 1 Feeler, assembled 1.077.185 11 1 Bolt, guiding 1 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121 - 07 14 1 Washer 1.077.121 - 07 15 1 Bracket (angle), with spring 1.077.130 14 1 Washer 1.077.130 15 1 Bracket (angle), with spring 1.077.330 16 Nut, hex 22.01.8040 1.077.331 18 1 Screw, collared 1.077.331 - 01	03	2	Nut, hex	22.99.0103
05 2 Washer 1.077.121-09 05 2 Washer 1.077.121-10 06 1 Bearing, ball 41.09.0102 07 2 Screw, shoulder 1.077.121-05 08 1 Ring, plain 1.077.121-04 09 1 Stud, threaded 1.077.121-06 10 1 Feeler, assembled 1.077.121-06 11 1 Bolt, guiding 1 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121-08 14 1 Washer 1.077.121-07 15 1 Bracket (angle), with spring 1.077.31 16 1 Nut, hex 22.01.8040 17 1 Washer 1.077.331 18 1 Screw, collared 1.077.331 19 1 Clevis 1.077.305 -08 53 1 Shaft with hole 1.077.305 -03	04	4	Cap, guiding	1.077.121 - 02
05 2 Washer 1.077.121 - 10 06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121 - 05 08 1 Ring, plain 1.077.121 - 04 09 1 Stud, threaded 1.077.121 - 06 10 1 Feeler, assembled 1.077.121 - 06 11 Bolt, guiding 1.077.121 - 08 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121 - 08 14 Washer 1.077.121 - 08 15 1 Bracket (angle), with spring 1.077.121 - 07 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331 19 1 Clevis 1.077.305 - 08 10 Saft with hole 1.077.305 - 03	05	2	Washer	1.077.121 - 09
06 1 Bearing, ball 41.99.0102 07 2 Screw, shoulder 1.077.121-05 08 1 Ring, plain 1.077.121-04 09 1 Stud, threaded 1.077.121-06 10 1 Feeler, assembled 1.077.121-06 11 1 Bolt, guiding 1.077.135 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121-08 14 1 Washer 1.077.121-07 15 1 Bracker (angle), with spring 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331-02 19 1 Clevis 1.077.305-08 10 Screw, hex, head dog point 1.077.305-03 10 Shaft with hole 1.077.305-03	05	2	Washer	1.077.121 - 10
07 2 Screw, shoulder 1.077.121-05 08 1 Ring, plain 1.077.121-04 09 1 Stud, threaded 1.077.121-06 10 1 Feeler, assembled 1.077.185 11 1 Bolt, guiding 1 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121-07 14 1 Washer 1.077.180 15 1 Bracket (angle), with spring 1.077.310 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331-02 10 1.024 is 1.077.331-02 10 Screw, heak head dog point 1.077.305-03 10 Screw, heak, head dog point 1.077.305-03 10 Shaft with hole 1.077.305-03	06	1	Bearing, ball	41.99.0102
08 1 Ring, plain 1.077.121 - 04 09 1 Stud, threaded 1.077.121 - 06 10 1 Feeler, assembled 1.077.185 11 1 Bolt, guiding 1.077.181 12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121 - 07 14 1 Washer 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Blacket (angle), with spring 1.077.330 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331 - 01 20 1 Screw, hex, head dog point 1.077.305 - 03 13 1 Shaft with hole 1.077.305 - 03	07	2	Screw, shoulder	1.077.121 - 05
09 1 Stud, threaded 1.077.121 - 06 10 1 Feeler, assembled 1.077.185 11 1 Bolt, guiding 2 12 1 Spring, tension 1.077.121 - 08 13 1 Spring, tension 1.077.121 - 08 14 1 Washer 1.077.121 - 07 15 1 Bracket (angle), with spring 1.077.121 - 07 16 1 Nut, hex 22.01.8040 17 1 Bracket (angle), with spring 1.077.330 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331 - 01 19 1 Clevis 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	08	1	Ring, plain	1.077.121 - 04
10 1 Feeler, assembled 1.077.185 11 1 Bolt, guiding 1 12 1 Sorew, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121 - 08 14 1 Washer 1.077.121 - 07 15 1 Bracket (angle), with spring 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.331 18 1 Screw, collared 1.077.331 - 02 19 1 Clevis 1.077.331 - 02 19 1 Clevis 1.077.331 - 03 53 1 Sorew, collared 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	09	1	Stud, threaded	1.077.121 - 06
11 1 Bolt, guiding 21.01.0354 12 1 Sprew, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121-08 14 1 Washer 1.077.121-07 15 1 Bracket (angle), with spring 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.330 From S 37751 + G 43228 1.077.331 18 1 Screw, collared 1.077.331-02 19 1 Clevis 1.077.331-02 19 1 Screw, head dog point 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	10	1	Feeler, assembled	1.077.185
12 1 Screw, machine, slotted head M 3 x 6 21.01.0354 13 1 Spring, tension 1.077.121-08 14 1 Washer 1.077.121-07 15 1 Bracket (angle), with spring 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.330 From S 37751 + G 43228 1.077.331 - 02 19 1 Screw, collared 1.077.331 - 02 19 1 Screw, hex, head dog point 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	11	1	Bolt, guiding
13 1 Spring, tension 1.077.121-08 14 1 Washer 1.077.121-07 15 1 Bracket (angle), with spring 1.077.180 16 1 Nut, hex 2201.8040 17 1 Plunger, complet 1.077.330 From S 37751 + G 43228 1.077.331 18 1 Screw, collared 1.077.331 - 01 20 1 Screw, hex, head dog point 1.077.305 - 08 13 1 Shaft with hole 1.077.305 - 03	12	1	Screw, machine, slotted head M 3 × 6	21.01.0354
14 1 Washer 1.077.121 - 07 15 1 Bracket (angle), with spring 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.330 From S 37751 + G 43228 1.077.331 - 02 18 1 Screw, collared 1.077.331 - 02 19 1 Clevis 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	13	1	Spring, tension	1.077.121 - 08
15 1 Bracket (angle), with spring 1.077.180 16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.330 From S 37751 + G 43228 1.077.331 18 1 Screw, collared 1.077.331 · 02 19 1 Clevis 1.077.305 · 08 53 1 Shaft with hole 1.077.305 · 03	14	1	Washer	1.077.121 - 07
16 1 Nut, hex 22.01.8040 17 1 Plunger, complet 1.077.330 18 1 Screw, collared 1.077.331 · 02 19 1 Clevis 1.077.331 · 02 10 Screw, hex, head dog point 1.077.305 · 08 53 1 Shaft with hole 1.077.305 · 03	15	1	Bracket (angle), with spring	1.077.180
17 1 Plunger, complet 1.077.330 From S 37751 + G 43228 1.077.331 - 02 18 1 Screw, collared 1.077.331 - 01 19 1 Clevis 1.077.331 - 01 20 1 Screw, hex, head dog point 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	16	1	Nut, hex	22.01.8040
From S 37751 + G 43228 1.077.331 18 1 Screw, collared 1.077.331 - 02 19 1 Clevis 1.077.331 - 01 20 1 Screw, hex, head dog point 1.077.331 - 01 33 1 Shaft with hole 1.077.305 - 03	17	1	Plunger, complet	1.077.330
18 1 Screw, collared 1.077.331-02 19 1 Clevis 1.077.331-01 20 1 Screw, hex, head dog point 1.077.305-08 53 1 Shaft with hole 1.077.305-03			From S 37751 + G 43228	1.077.331
19 1 Clevis 1.077.331 · 01 20 1 Screw, hex, head dog point 1.077.305 · 08 53 1 Shaft with hole 1.077.305 · 03	18	1	Screw, collared	1.077.331 - 02
20 1 Screw, hex, head dog point 1.077.305 - 08 53 1 Shaft with hole 1.077.305 - 03	19	1	Clevis	1.077.331 - 01
53 1 Shaft with hole 1.077.305 - 03	20	1	Screw, hex, head dog point	1.077.305 - 08
	53	1	Shaft with hole	1.077.305 - 03

Page 85

INDEX	QTY	PART NAME	ORDER NUMBER
F		Brake System
01	1	Chassis, brake
02	3	Screw M 3 x 6	21. 01.0354
03	3	Washer, lock	24. 99.0105
04	1	Lever, brake	1.077.411
05	1	Lever, brake	1.077.415
06	1	Spring, helical	1.062.210 - 06
07	2	Band, brake	1.077.420
80	2	Spring, helical, brake	1.077.100 - 13
09	6	Clip, re taining Ø 3.2 mm	24. 16.3032
10	1	Solenoid ( without plunger )	1.014.750
11	1	Plunger, with collar screw & retainer	1.014.708
12	2	Screw M 4 x 5 (length 5 mm max !)	21. 01.0453
13	2	Washer	24. 99.0106
14	2	Motor, reel (see G - motor, reel)	1.077.280
15	2	Spacer	1.077.100 - 06
16	2	Washer, height adjustment ( according to need )	1.736.502 - 04
17	2	Washer, star	24. 16.6080
18	2	Drum, brake, with lining & star washer	1.077.560
		Lining, brake ( by the meter )	89. 01.0155
19	2	Washer	23. 01.3043
20	2	Spring, belleville	37. 01.0103
21	2	Screw, hex head M 4 x 8	21. 01.4455
22	2	Turntable, metal	1.077.564
22a
23	6	Screw M 3 x 8, Ni-plated	21. 02.0355
24	2	Shaft section, 3 - prong	1.077.568 - 03
25	2	Spring, compression	1.736.794 - 03
26	2	Screw, shoulder	1.077.568 - 02
27	8	Screw M 4 × 8	21. 01.0455
28	1	Counter	1.077.100 - 09
29	1	O - Ring	31. 99.0106
30	1	Bolt, threaded	1.077.100 - 19
31	1	Cap, rubber	1.077.100 - 20
32	1	Screw M 3 x 8	21. 01.0355
33	2	Washer, flat	23. 01.2032
		Washer, lock, helical 24. 99.0107

10.72

Page 86

Page 87

INDEX	QTY	PART NAME	ORDER NUMBER
G		Motor, Reel
		In care of a defective states, rates, or shaft, evaluates motor
		( See also E - Brake System )

	1	Motor, reel, assembled
01	1	Clip, spring	24. 99.0111
02	1	Ring, retaining, external Ø8 mm	24. 16.5080
03	2	Bearing, ball EL8 608	41. 99.0105
04	2	Ring, retaining, ( internal Ø 22 mm )	24. 16.4220
05	4 - 6	Spring, belleville put in only enough springs till axial	37. 02.0103
		play is taken up
















			2








2

Page 88

INDEX	ΩΤΥ	PART NAME	ORDER NUMBER
G 1		Motor, Reel
		In case of a defective stator, rotor, or shaft, exchange motor. (See also F — Brake System).
	1	Motor, reel, assembled	1.021.205
01	1	Clip, spring	24.99.0111
02	1	Ring, retaining, external ( ø 8 mm)	24.16.5080
03	2	Bearing, ball EL 8 608	41.99.0105
04	2	Ring, retaining, (internal ø 22 mm)	24.16.4220
05	2	Spring, belleville	37.02.0206

On reel motors of the type 1.021.200 the shaft lock must not be removed.

Page 89

Page 90

INDEX	X QTY PART NAME		ORDER NUMBER
J		Capstan motor with sleeve bearings Modification effective from serial No. S 60483 and G 78003
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17	1 1 3 2 1 1 2 1 1 2 1 2 1 2 4	Motor, capstan, assembled Rotor Shaft, capstan Cap, plastic Ring, felt Bearing, sleeve must not be removed Ring, spacer Bearing, thrust Washer, low-friction Spring, belleville Ring, retaining, internal Shield Screw (M3 x 4) Head, pick-up Washer, antivibration Screw (M3 x 6) Washer, plain	1.021.160 1.021.161 1.021.160.12 1.077.220-02 1.077.220-01 1.021.160-08 1.021.162 1.021.160-09 37.02.0106 24.16.4220 1.077.200-03 21.01.0352 1.077.240 1.077.200-04 21.99.0117 23.01.1032
18 19 20	4 1 1	Screw (M4 x 30) Plate, screening Clip, shaft	21.01.0464 1.077.100–22 1.021.160–10
		7,5/15 ips Recorder: Motor, capstan, assembled, 7,5/15 ips shaft, capstan 7,5/15 ips	1.021.165 1.021.165.05

Page 91

Page 92

12.1. REVOX A77- DOLBY

12.1.1. Introduction

The DOLBY B Type Noise Reduction System is based on the same principles as the professional DOLBY A System, but is simplified and economical to permit its application in consumer tape recorders. The system is designed to reduce tape hiss by increasing the level of low-level signals in a variable range of high frequencies during recording, and automatically reducing the level during playback of the same locations in the program. Although no change is then heard in the original signal, the attenuation during playback results in a reduction of tape hiss. The amount of noise reduction achieved is approximately 10 dB (DIN weighting).

The basic Dolby B circuit can be switched to make it operate in either the "record" or "play" mode. For many applications, therefore, it is possible to work with one switchable record-play processor per channel. However, in order to allow simultaneous recording and monitoring of Dolby-processed tapes and track-to-track transfer of Dolby recordings, the Dolby version of the Revox A77 is equipped with separate recording and playback processors for each channel.

Because of the limited space available in the Revox A77, the plug-in power amplifiers cannot be accomodated in the Dolby version.

In order to realize the full subjective improvement in signalto-noise ratio which the Dolby System can provide, it is essential that noise and hum in the program and other components used be substantially below the level of the tape hiss, since these noises, like all sounds of any kind which are part of the original program, will not be reduced or audibly affected in any other way by the Dolby System. Because the Dolby B System reduces noise only above 200 Hz, it is particularly important that low-frequency noise and hum be as low as possible. To avoid amplitude distortion when working with the Dolby System, the tape recorder must have a very linear frequency response.

12.1.2. Circuit Operation Record Processor 1.077.853

In addition to the actual processor, this printed circuit board also contains amplifiers and filters for each channel plus a calibration oscillator which is common to both channels. This oscillator is coupled to the input of each channel by separate 1 Mohm resistors. Power is supplied to the oscillator when the front panel switch is set to the "calibrate" position. The oscillator level is adjustable by means of potentiometer P 103 r which is pre-set at the factory. The oscillator frequency is approximately 800 Hz.

The signal at input 5(11) is amplified by Q1, Q2 from 9 mV to 200 mV.

Low-level Frequency Response Characteristics of Record and Play Processors

Fig. 12.1.-1.

From there it passes through the filter formed by L1, L2, C3–C7 which is intended to suppress interference from multiplex signals when recording stereo FM broadcasts. Furthermore, any unwanted signals above 20 kHz (e.g., residual bias and erase oscillator signals) are sufficiently attenuated by the active low pass filter built around transistor Q4 that they cannot upset the operation of the dynamic filter section of the noise reduction circuit. If the multiplex filter with its cut-off frequency of 14.5 kHz is not required, it may be disabled by a relay which operates on both channels. The audio signal at the output of the low pass filter Q4 is divided into a main channel and a side channel.

The main channel feeds the signal via R42 and the emitter follower Q9 directly to the output 1 (13).

In the side channel, the signal passes through the dynamic high pass filter formed by C11, R19, C12 and the drainsource path of FET Q5. When low-level signals are present, the FET is non-conductive and has a high drain-source resistance, so that only the first section of the filter C11, R 19 controls the response of the side chain. The output from this filter is then amplified by Q6, Q7 and recombined with the main signal at Q9 via the resistor R 41.

The gain of the side chain is so adjusted that at - 40 VU, the combined signal at the output of Q9 is increased by 10 dB at 5 kHz. The graphs in Figure 12.1.-1. show the frequency response for low-level signals. The side-chain output signal is also fed to transistor Q8 where it is amplified, and then rectified and smoothed by the nonlinear integrator D4, D5, R34, R36, C20, C21, the resulting D.C. voltage being returned to the gate of FET Q5.

Page 93

Record Processor Characteristics

Low-level Frequency Response Characteristics of Record Processor under High-level Signal Conditions

Fig. 12.1.-2.

If a higher audio signal causes the D.C. voltage on the gate to exceed the bias point of the source – which is set with P 101 r(law control) – the drain-source path will become conductive. This then results in a change of the turn-over frequency of the second high pass branch formed by C12 and the drain-source resistance. With increasing input level, the proportion of the side channel signal added to the mainchannel signal will become smaller, resulting in a frequency characteristic as shown in Figure 12.1.–2.

At 0 VU, the side channel component has become so small that the main signal will appear practically unaltered at the output, that is, it has a linear frequency characteristic.

The variable filter action is shown in Figure 12.1.-3. It shows the amplitude characteristics of test signals at different frequencies and at a low level (-42 VU, which is below the threshold of the compressor) in the presence of 0 VU signals of various frequencies which drive the compressor into gain reduction. When comparing this with a filter of fixed bandwidth, one will note that marked noise reduction is obtained at high frequencies in the presence of high-level signals of lower frequency.

A two-stage non-linear integrator is used in the side chain to avoid the generation of modulation products on transients.

For small signal level variations, diode D5 is non-conducting, so that the time constant of the RC combination R39, C24, provides considerable smoothing effect. On a sudden increase, however, D5 becomes conductive and quickly lowers the gain of the side chain. For large amplitude transients, the attack time will be reduced to 1.5 milliseconds, approximately. To avoid overshoots in the output during this interval, two clipping diodes D2, D3, are provided which respond to extreme transients only until the side chain has returned to its original operating point. As a result, the signal appearing at the output consists of a large amplitude undistorted main signal mixed with a small amplitudeclipped side chain signal. The distortion of the output signal is therefore small, and as the effect lasts for so short a time, inaudible.

Fig. 12.1.-3.

To prevent the erase oscillator from interfering with the control circuit, the gain of Q8 is greatly reduced at the frequency of the erase oscillator by the parallel resonant circuit L3, C22. Capacitors C19 and C20 give additional attenuation.

Playback Processor 1.077.852

The same basic circuit is used for the playback processor, but instead of the side chain being fed from the input, it is fed from the output. Furthermore, the phase of the output signal ( and hence of the side chain signal ) is opposite to that of the input so that the side chain forms a negative feedback element, and produces replay characteristics which are complementary to the record characteristics.

The playback processors for both channels are contained on one plug-in printed circuit board. In addition, this board contains the VU meter amplifier Q9, used for matching the the 100 m V levels to the VU meters. Potentiometer P 103 p adjusts the gain of that stage.

The signal arrives from input 9 (13) and is amplified by Q1, Q2, Q3 from 40 mV to the Dolby Level of 100 mV. The voltage divider formed by R14, R15, matches the output signal to the A77 internal operating level of 9 mV which then appears at point 11 (14).

In order to be able to work without Dolby noise reduction, the side chain signals can be shorted out by Q4, in the playback processor and by Q3 in the record processor. Both devices are activated by the Dolby "In- Out-" switch root on the front panel of the recorder.

Page 94

12.1.3. Use of the Dolby Circuit in the Tape Recorder

To achieve correct performance both the record and playback sections must work at identical levels, that is, the tape recorder must have unity gain and a very linear frequency response from the output of the record processor to the input of the playback processor. All Dolby-encoded tapes must be recorded with the operation of the noise reduction circuitry referred to an absolute level of tape flux. Because the same flux level is also standardized for playback, interchangeability of Dolby-encoded tapes is assured. The standard tape flux is 185 nWb/m which corresponds to the Ampex Reference Level on Ampex calibration tapes with NAB equalization.

Any change in gain between the output of the record processor and the tape would be equivalent to a shift in the processor's characteristics. Differences in tape sensitivity must therefore be balanced out, using the RECORD CALIBRATION () / () control provided on the front panel for this adjustment.

Fig. 12.1.-5.

on/off-tape monitor selector
13 Record volume control Ch I
Record volume control Ch II
Record pre-selector Ch I
B Record pre-selector Ch II
DOLBY IN/OUT Switch to activate or to deactivate the DOLBY noise reduction circuits.

RECORD CALIBRATION

6 Record Calibration for Channel I
B Record Calibration for Channel II
FILTER IN/OUT Switch for turning the multiplex filter on or off.

Adjustment of REC CAL Control

1. Load the recorder with tape of the kind to be used.
2. Set record level controls (1)/ (1) to zero.
3. Turn selector switch 😰 to CAL.
4. Set the recorder to RECORD.
5. Adjust REC CAL controls 6 / 1 until each meter reads
6. Return selector switch 1 to INPUT or TAPE.

Be careful not to accidentally select the CAL position during source-tape switching while recording, or the calibration oscillator tone will be superimposed upon the signal being recorded.

Index Numbers

The index numbers 50 to 53 are used for identifying the additional operating controls on the DOLBY equipped RE-VOX A77 tape recorder. All other index numbers make reference to the operating instructions for the standard version except for the following changes:

Standard Recorder

DOLBY Version

Button Speakers off 🗿 Button Reel Motors off 😰

Monitor selector (1):

Position NAB
Position IEC

corresponds to TAPE replaced by Calibrate (new function)

Page 95

Mismatch Response: 2 dB Gain Between Record and Play Processors

Mismatch Response: 2 dB Loss Between Record and Play Processors

Fig. 12.1.-6.

12.1.4. Matching and Mismatching

The frequency response of a record/playback processor chain connected in series hould be within a tolerance of ± 1 dB. Typically, deviations much smaller than this are achieved. Although mismatching may arise from a number of causes, most commonly it is the result of incorrect adjustment of the signal channel between the record and playback processors for unity gain, either on a wide-band basis or at high frequencies. The effect of such gain errors (wideband) are shown in Figures 12.1.-6. and 12.1.-7. Under dynamic program conditions, response deviations of this magnitude are inaudible.

Other sources of error are incorrect alignment or a build-up of component tolerances. Individual variations in FET's are mainly responsible for errors in the processor characteristics.

It can be seen that the region most sensitive to mismatch is that at a level of about -25 VU; the error will be less at higher and lower levels.

Basic Printed Circuit Board 1.077.854

This board carries both plug-in processors and all of the required interconnections. Also on this board is a Zener diode to derive the + 7.2 V from the 21 V supply and an RC combination to filter out any hum in the + 27 V supply for the relay in the record processor.

All interconnections between the switch board and the printed circuit cards carrying the calibration potentiometers, the power supply, the VU meters and the switches "Dolby in/out", "Filter in/out" and "Calibration" are either soldered or plugged onto this board.

Fig. 12.1.-7.

Calibration Potentiometer Board 1.077.342

Two potentiometers are mounted on this board for individual front panel adjustment of both record channels to match them to tapes of different sensitivity.

Switchboard 1.077.426

This differs from the corresponding board in the standard version of the A77 in that it carries the pluggable inputs and outputs for the Dolby processor. The NAB/IEC switch has been modified to carry the function of switching the VU meters for metering level from the tape as well as the signal from the record amplifier which is normally metered during recording. Equalization characteristics remain NAB in all three positions of the monitor selector (Tape-Input-Calibration).

Power Transformer 1.077.524

The transformer differs from the standard version in that the wire of the winding for the regulated 21 V supply has been changed from 0.5 mm diameter to 0.9 mm. Both 32 V windings for the power amplifiers have been omitted.

Reel Motors Off Switch

This switch had to be omitted and the two record calibration potentiometers are installed in its place.

VU Meter Level

VU calibration is effected on the DOLBY playback board. The calibration controls in the A77 record amplifiers are disabled.

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Reproducer Test Tapes NAB 7 1/2 ips for REVOX A77 Dolby 50/3180 μsec (recording of Nov.30 1971)

The tapes contain the following frequencies and levels:

1 kHz 30 s AMPEX Operating Level 1 kHz 8 s - 10 dB 10 kHz 60 s - 10 dB Frequency response test section: all levels - 20 dB 8 sec. 1k, 40, 63, 125, 250, 500, 1k, 2k, 4k, 6,3k, 8k, 10k, 12,5k, 14k, 16k, 18k 1k - 10 dB

DIN 19 S (70 µsec) Standard Test Tape issue 1970, No. 5608 was used as the frequency response reference. An Ampex Test Tape (Nov. 71) was used as a level reference.

To obtain the correct frequency response the following correction factors were used (70 µsec. to 50/3180 µsec).


40	Hz	+ 3,6 dB
60		+ 1,8
125		+ 0,1
250		- 0,4
500		- 0,2
1	k	0
2		+ 0,7
4		+ 1,7
6,3		+ 2,1
8		+ 2,3
10		+ 2,4
12		+ 2,5
15		+ 2,5

The DIN Standard Test Tape was used because the Ampex tape contains different frequencies and it does not extend beyond 15 kHz.

REVOX A77 with DOLBY Noise Reduction System, Additional Technical Data

All measurements taken with REVOX 601 tape, DOLBY electronics switched on.

2-Track Version (values for the 4-Track Version are shown in parenthesis)

Signal to Noise Ratio, off tape, weighted as per CCIT:

At 7 1/2 ips. better than 67 dB (65 dB) At 3 3/4 ips. better than 64 dB (62 dB)

Weighted as per ASA A:

At 7 1/2 ips. better than 70 dB (67 dB) At 3 3/4 ips. better than 67 dB (65 dB)

Distortion measured off tape, 500 Hz Peak Level (assumed to be +6 VU)

At 7 1/2 ips. better than 1.0 % (1.5 %) At 3 3/4 ips. better than 1.5 % (2.0 %)

Operating Level 0 dB (100 %):

At 7 1/2 ips. better than 0.5 % (0.5 %) At 3 3/4 ips. better than 0.5 % (1.0 %)

All other performance data are identical with the data for the standard version of the A77 recorder.

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ALI	ALIGNMENT INSTRUCTIONS REVOX A 77 DOLBY
Hem	Operation	Alignment Procedure	Test Equipment	Tape Speed ips	Frequency	Voltage	Testpoint	Where to adjust
1.	Adjustment of regulated- Voltage	Adjust exactly to nominal 21 volts	Multimeter	7.5		+ 21 V DC	Yellow wire ED 1	P 106
2.	Adjustment of Tacho Head (S.M. 6.2.1.)	Alter head position to obtain specified tacho voltage	Electronic Volt- meter	3.75		40 m V AC	E1 — E2	mounting screws of tacho-head
3.	Bias-Filter record (S.M. 6.4.3.)	Adjust for minimum voltage	Electronic Volt- meter	7.5	120 kHz	< 300 mV	see fig. 6.4.—63/64	L 501
4.	Bias-Filter, replay (S.M. 6.4.4.)	Adjust for minimum voltage	Electronic Volt- meter	7.5	120 kHz	< 50 mV	Wiper P 801	L 801
5.	Motor Speed (S.M. 6.2.2.)	Adjust tacho frequency (mea- sure over at least 10 sec.)	Digital Counter	7.5 3.75	1601 Hz 800 Hz	10 V	Pin 2 on T 201	T 201 P 201
6.	Oscillator and Bias adjust	As per Service Manual 6.4. Adjust dummy load	Electr.Voltmeter Digital Counter Digital Counter	7.5 7.5 7.5	120 kHz 120 kHz ± 5 kHz 120 kHz ± 5 kHz	2 Track 21 VAC	HB3-HB6 HB3-HB6 HB3-HB6	blue & orange wire Dummy load L 601
7.	DOLBY record adjustments	Turn FET-bias off, set gain control to minimum amplification						P 101 r (CH I, CH II) P 102 r (CH I, CH II)
	DOLBY "OUT"	DOLBY switch in position "OUT"
		Connect Audio Generator to "AUX" inputs,	T19		5 kHz	∿ 0.45 mV		Generator
	DOLBY "IN"	Adjust level on Generator Adjust level on Generator	T 19 VTVM		5 kHz	3 mV 2.6 mV	P1, P2 P3, P4	Generator Generator
		measure voltage rise on DOLBY output	T 19 VTVM		5 kHz	∿ 7 mV (+8 dB)	P3, P4
		Level adjustment	T 19 VTVM		5 kHz	8.2 mV (+10 dB)	P3, P4	P 102 r
		Level reduction by 2 dB	T 19 VTVM		5 kHz	-2 dB	P3. P4	P 101 r
8.	DOLBY replay adjustments	Turn FET bias off, Set gain control to min. amplification.						P 101 p (CH I, CH II) P 102 p (CH I, CH II)
	DOLBY "OUT"	DOLBY switch 😳 in pos. "OUT" Connect Audio Generator to DOLBY inputs (with test clips).	Т 19		5 kHz		P5, P6
	DOLBY "IN"	Adjust level on generator DOLBY switch 😨 in pos. "IN"	T 19 VTVM		5 kHz	7.6 mV	P7, P8
		Adjust level reduction on DOLBY outputs	T 19 VTVM		5 kHz	—10 dB = 2.4 mV	P7, P8	Р 102 р
		Level increase by 2 dB	T 19 VTVM		5 kHz	+ 2 dB = 3 mV	P7, P8	P 101 r
9.	VU-Meter calibration	Connect Audio Generator to "AUX" inputs,	T 19 or generator		1 kHz	∿ 13 mV
		Calibrate VU-meters			1 kHz 1 kHz	100 mV 0 VU	P1, P2	Р 103 р
10.	Balance Adjustment
11.	Playback head azimuth adjustment	As per Service Manual sections 6.3.1. and 6.3.2.	DOLBY reference tape
12.	Playback level off test tape	Playback level calibration	VU-Meter	7.5		185 nWb/m = 0 VU		P 801 print 077.720
13.	Frequency response check	As per Service Manual 6.3.4. and additional instructions.
14.	Record head azimuth adjustment	"REC. CAL" pot-meters ⓓ /☜ fully ccw. T19 generator level (∿13 mV) adjusted for 0 VU indication. Reduce generator level -20 dB Adjust azimuth as per S.M. 6.5.3.			10 kHz 10 kHz	VU = 0 dB 20 dB
15.	RF Bias Adjustment	As per Service Manual 6.5.2.	T19	7.5 3.75		4 dB 5 dB	OUTPUT CH I, CH II

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						-
16.	Record Level and calibration	Depress button –6 dB on T19,	T19		1 kHz
	oscillator adjustments	T19 Adjust generator to read	VU Meter			— 1 dB
		-1 dB on both VU-Meters	Commenter
		fully ccw, increase generator level,	Generator			+10 08
		Monitor selector 🙆 in position "TAPE"	VU Meter			0 dB		"REC.LEVEL" Potmeter ()/()
		Switch to record and adjust potentiometer P503 (record amplifier 1.077.705) to 0dB on VU-Meter.
						10.10
		Reduce Generator Level Baise record level	Generator VU-Meter			-10 dB		"REC.CAL" potmeter 6 /69
		"REC.LEVEL" Potmeter fully
		ccw, turn monitor selector	VU-Meter			0 dB		P 103 r
		adjust calibration oscillator
17.	Checking the DOLBY	Reduce T19 generator level	T19			-20 dB
	Frequency Response	by 20 dB, Turn DOLBY switch 👩 to
		position "IN"
		Frequency response	T 19 VTVM	7.5	30-20000 Hz	+ 2/3 dB	OUTPUT
		tolerances		3.75	30-16000 Hz	+ 2/3 dB	OUTPUT
		Louis difference Manage Otomore			50-10000 Hz	± 1,5 dB	OUTPUT
		Attenuation of MPX-filter			18 kHz	- 25 dB	OUTPUT
18.	Checking the Output Level	T19 generator at 1 kHz	T 19		1 kHz
		Adjust record level to 0 VU	T 10 1/T1/04			E60mV + 1dP	Radio Output
		Level difference Mono-Stereo	I IS VIVIN			<1 dB
19.	Distortion Measurement	Measure 3rd harmonic	T19 distortion	7.5	1.5 kHz	+ 6 dB	1.5 %
			analyzer	3.75	1.5 kHz	+ 6 dB	2 %
				3.75	1.5 kHz	0 00	1 %
		Values independent of DOLBY
		switch position				Atrack	2-track
20.	Noise measurement off tape	DOLBY-switch 🚳	T19	3.75	unweighted	-53 dB	2-track
	weighted/unweighted	position "IN"		7.5	weighted	-62 dB	-64 dB
				1.0	weighted	-65 dB	-67 dB
		DOLBY-switch 50		3.75	unweighted	-52 dB
				7.5	unweighted	-55 dB
		weighting characteristics as per CCIT			weighted	-56 dB
21	Amplifier noise	Becorder in "PLAY" mode.
	(without tape)	all noise readings with reference
	weighted/unweighted	To +6 VU, Tolerances:		7.5	unweighted	> 58 dB
				0.75	weighted	> 68 dB
				3.75	unweighted weighted	> 58 dB > 64 dB
		Monitor selector 🔞 in position "INPUT"				> 75 dB
22.	Crosstalk rejection MONO	As per S.M. 6.6.5., adjust
		between DOLBY IN and DOLBY OUT.
23.	Crosstalk rejection STEREO	As per S.M. 6.6.6.
24.	Erase efficiency	As per S.M. 6.6.4.
25.	Final check	MONO-STEREO switch,
		track to track transfer, input sensitivity, noise voltage, S/N ratio
		in pos. "MICRO" (> 45 dB)
		mechanical inspection

Page 99

Function Diagram A77 DOLBY

Page 100

Block Diagram A77 DOLBY

PLAYBACK PROCESSOR