AWA 609T, 707C, 803G Diagram

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Page 1

(4) 12.0-9.4 Mc. ................................. (5) 15.0-11.7 Mc. ...... (20.0-25.7 M.)
(6) 19.0-15.0 Mc. (15.8-20.0 M.)
(7) 22.3-17.7 Mc. ................................

INTERMEDIATE FREQUENCY 455kc.

POWER SUPPLY RATING .... 200-260 V. A.C., 50-60 C.P.S. (Models are produced with other voltage and frequency ratings.)

POWER CONSUMPTION .... 80 watts

(3) 6U7G I.F. Amplifier.

LOUDSPEAKER:

Model 609-T: 7 inch-Code No. AW19. Transtormer-XAI. 1100 ohms. V.C. Impedance—3 ohms at 400 C.P.S.
(5) 6V6GT/G Output (6) 5Y3GT/G Rectifier.

Models 707-C, 803-G: 12 inch—Code No. AS17. Transformer-TXI Field Coil Resistance-1500 ohms. V.C. Impedance—12.5 ohms at 400 C.P.S.

UNDISTORTED POWER OUTPUT ...... 4.2 watts

DIAL LAMPS (3)

......................................

NOTE.—The three models covered in this booklet employ chassis of similar type, but which differ in the following details:— Table Model 609-T-Power transformer secondary volts suitable for 1100 ohms loudspeaker field.

Console Model 707-C—Power transformer secondary volts suitable for 1500 ohms loudspeaker field. Combination Model 803-G—Identical with 707-C chassis with the addition of a 3 point socket for phono, motor mains connection.

Page 2

TUNING CIRCUIT DIAGRAM.

Page 3

PHONO. MOTOR AUTOMATIC STOP ADJUSTMENT.

The patent stop and switch is fully automatic.

As the needle travels towards the centre of the record, the pick-up arm moves friction plate A, which, through the friction pad and spring, carries with it the main lever B and trip lever C.

This main lever moves in towards the turntable spindle, on which is mounted the striker, which gently wipes against the rubber bush on end of trip lever C at each revolution, thus tapping back the main lever B (the friction between lever A and lever B allows this).

The "tapping back" process continues until the needle reaches the "run-in" groove in the centre of the record. The trip lever is now moved forward into the path of the striker, which strikes the side of the lever and trips the stop mechanism.

If stop fails to operate at tinish of record, there is probably insufficient friction between lever A and lever B. This may be rectified by turning the friction screw in lever B in an anti-clockwise direction. If there is still insufficient friction, it may be that oil is present on the felt friction pad. If so, remove the pad and wash it in petrol to remove the oil.

When stop operates early, i.e., before needle reaches the end of the record, the trouble is either due to excessive friction or to the rubber bush on the trip lever being worn. Friction can be reduced by turning the friction screw clockwise.

As this adjustment is very sensitive, the screw should not be turned more than a quarter of a turn at a time. Excessive friction may cause a knocking sound to be heard in the loudspeaker and undue wear on the records.

When the rubber bush is worn, this may be turned round on its pin to expose a new face to the striker.

AGRAM OF AUTO SWITCH FITLED TO TYPE E RADIOGRAM UNIT

SOCKET VOLTAGES AND CURRENTS

C Valve.	ontrol Grid to Chassis Volts.	Cathode to Chassis Volts.	Screen Grid to Chassis Volts.	Plate to Chassis Volts.	Plate Current mA.	Heater Volts.
6U7G R.F. Amp., M.W.	-3.9*	0	95	255	7.0	63
S.W	-3.5*	0	95	255	7.0
6J89 Converter, M.W.	-3.9*	0	95	255	0.8	63
S.W.	-4.5*	о	95	255	0.6-0.8
Oscillator, M.W.				150	5.0
S.W				150	5.0
6U7G I.F. Amp., M.W.	-3.9*	0	95	255	7.0	63
S.W	-3.5*	0	95	255	7.0
6G8G/6B8G Detector	-1.5*	0	30*	125*	0.5	63
6V6GT/G Output	0	12.5	255	245	44.0	63
5Y3GT/G Rectifier	700/350 V.	, 80 m.A.	Total Curi	rent Drain		5.0

Measured with receiver connected to 240 volts A.C. supply.

Volume Control at maximum. No signal input.

* Cannot be measured with ordinary voltmeter.

MECHANICAL REPLACEMENT PARTS.


ltem.	Part No.
Cabinet, console	C69
Cabinet, combination	C46
Cabinet, table	C67
Cable, band indicator	19150
Cable, loudspeaker	19087
Cable, pick-up	19086
Cable, power	209
Cable, power switch	19089
Cable, volume control	19085
Chassis end, right hand	10000
left hand	9875
Clip, grid	745 9
Cone assembly, loudspeaker
Туре АШ19	9356
Type AS17	9332
Core, magnetite, small	11403
large	11400
Dial frame assembly	19082
Dial scale	19100
Drum, band indicator	19094
Drum, drive	9090
Dust cover, loudspeaker—
AW19	9843
AS17	10306
Knob	4589

ltem.	Part No.
Knob, range switch	5846
Knob, tuning	8075
Mount plate assembly, tuning drive	17816
Pulley, brass	7885
Screen, I.F. transformer	3351
сар	8372
Screen, valve	8147
Сар	8148
register	4733
Socket, dial lamp	4194
Socket, valve	4704
Socket, valve, cushion	7326
Spindle, tuning drive, table	17739
console	9812
Spindle range switch extension table	19066
console	19584
Spindle tuning control extension	10507
Spinale, running control extension	17303
spring, band indicator	8364
opring, drive tension	6641
strip, tag, I way	7628
2 way	8863
3 way	9877
7 way	9879
Washer, felt	4935.

Page 4

MECHANICAL SPECIFICATIONS.

	Height.	Width.	Deptn.
Cabinet Dimensions (inches)—
Table	12	26
Console	32 1	33	13
Combination	32	36	16
Chassis Base Dimensions (inches)	3 1	16	7 1

Overall Chassis Height	•••••	9
Weight (nett Ibs.)—
Table		39
Console	•••••	84
Combination	•••••	150
Cabinet Finish	Walnut V	/eneer

CIRCUIT ARRANGEMENT.

6U7G—VI.

The 6U7G is a triple grid, super control R.F. amplifier and is utilised for this purpose. The output of the aerial coil, which is tuned to signal frequency by the aerial section of tuning capacitor, is applied to the control grid for amplification. The cathode being earthed, a minimum negative bias voltage of 3.9 volts is obtained from the back bias circuit, and applied to the control grid via the A.V.C. line. Amplification is also controlled automatically, due to functioning of the A.V.C. circuit.

6J8G—V2.

The 6J8G is a triode-heptode converter and is employed as a frequency converter. Voltages at signal frequency are applied to the control grid from the R.F. amplifier via the R.F. coil and associate circuit. Local oscillations are provided by the triode portion of this valve operating as a tuned grid feedback circuit comprising oscillator coil, padding capacitor and oscillator section of ganged tuning capacitor. Electronic mixing gives a resultant heterodyne frequency of 455 kc/s. The cathode of this valve being earthed, bias voltages are applied to the control grid via the A.V.C. line from the back bias circuit. Minimum bias on medium wave is -3.9 volts and short wave -4.5 volts. The 6J8G is not A.V.C. controlled on short wave.

Alignment should be necessary only when adjustments have been altered from the factory setting or when repairs have been made to the tuned circuits. Climatic conditions should not seriously affect the receiver.

It is important to apply a definite procedure, as given in this booklet, and to use adequate and reliable test equipment. Instruments ideally suited to the requirements are either the A.W.A. Junior Signal Generator type 2R3911, or the A.W.A. Modulated Oscillators type J6726 and C1070*. An output meter is necessary with both these instruments, the recommended type having an output impedance of 5000 ohms and a range of 5-3000 milliwatts. The meter should be connected across the primary of the loudspeaker transformer with the voice coil of the loudspeaker open-circuit. If the output meter used is one which does not impress a load on the anode circuit of the output valve it will not be necessary to open-circuit the voice coil.

As the calibration of the band-spread bands requires great accuracy, it is recommended that an A.W.A. Crystal Calibrator, type 6795, be used after setting the oscillator calibration to check the accuracy of the signal generator. The crystal calibrator emits a modulated signal at intervals of either 100 or 1000 kc/s, throughout the radio frequency spectrum, thus providing a series of fixed and equally spaced calibration points of known accuracy. When using this instrument care should be taken to select the correct signal. With the crystal set at the 1000 kc. position, a spurious image signal can generally be obtained by turning the tuning control of the receiver to a point approximately 100 kc/s, higher in frequency. This is a useful check as to whether a harmonic or spurious image is being tuned. If a crystal calibrator is not available, broadcasting stations of known frequency may be used as an alternative.

6U7G—V3.

The output from the 6J8G is coupled to the control grid of the 6U7G by the first I.F. transformer, which is permeability tuned to 455 kc/s. Bias conditions are similar to those of the 6U7G R.F. amplifier (VI).

6G8G/6B8G----V4.

The second I.F. transformer, permeability tuned to 455 kc/s, couples the output of V3 to the diode of V4 for detection. Portion of the R.F. voltage from this diode is fed to the A.V.C. diode by coupling capacitor (C44) and, in conjunction with diode load resistor (R10), develops a voltage which is applied to the A.V.C. controlled grids via the A.V.C. line. The A.V.C. voltage so developed varies in proportion to the strength of carrier being received. The audio component across the volume control is applied to the pentode section of V4 for amplification.

Valve types 6G8G/6B8G are interchangeable in this circuit.

6V6GT-----------------------------------

The 6V6G is a tetrode power amplifier which is resistancecapacity coupled to V4, and is automatically biassed. A negative feed-back tone control is employed. The output of the valve is coupled to the loudspeaker by the transformer T2.

5Y3GT------------------------------------

The 5Y3GT is a full wave high vacuum rectifier and supplies the D.C. requirements of the receiver.

ALIGNMENT PROCEDURE.

When using a signal generator or modulated oscillator with the tuning of the receiver fixed, two frequencies can be tuned from the test instrument, one 0.92 Mc/s higher in frequency than the other. In all cases the desired frequency is the lower of the two.

A convenient alignment jig designed to hold the receiver chassis and fitted with a dial scale and pointer may be obtained from the Service Department of the company. With this jig alignment may be carried out with the chassis coupled to an actual scale, thus ensuring that the calibration will be correct when the chassis is placed in the cabinet; otherwise, use the 0-180° calibration scale on the drum. (See alignment table.)

For all alignment purposes connect the "low" side of the signal generator to the receiver chassis.

Perform alignment in the proper order as shown in the chart, starting from No. 1 and following all operations across, then No. 2, etc.

Keep the volume control set in the maximum clockwise position and regulate the output of the test instrument so that a minimum signal is introduced to the receiver to give a standard indication on the output meter. This will avoid A.V.C. action and overloading.

When the receiver has been satisfactorily aligned, seal the adjusting screws with a small quantity of cellulose cement.

* If a type J6726 or C1070 instrument is used, see that a 250,000 ohm resistor is connected between the output terminals, and for short wave alignment a 400 ohm non-inductive resistor in series with the active output lead.

Page 5

CIRCUIT CODE

4	Circuit Code N	o. Description	Stock Code or Part No.	Circuit Code 1
1		INDUCTORS.		R18
÷.	LI, L2 LI, L2, LI, L2,	Aerial Coil 22.3-17. L3 Aerial Coil 19.0-15. L3. 14	.7 Mc. 9852 .0 Mc. 9852	R 19 R 20
	LI, L2,	Aerial Coil 15.0-11 L3, L4, L5—	.7 Mc. 9852	R21
1000	L6, L7	Aerial Coil 12.0-9.4 Aerial Coil 9.7-3.6	4 Mc. 9852 Mc. 9854	R22 R23
	L9, L10 L11	Aerial Coil Broadca R.F. Coil 22.3-17.7	ast 9748 Mc. 9853	R24 R25
300 (N × - 4	LII, LI2 LII, LI2	R.F. Coil 19.0-15.0 , L13 R.F. Coil 15.0 11.7	Mc. 9853	R26 R27 R29
-4	LII, LI2	R.F. Coil 12.0-9.4	Mc. 9853	R29
	LI5 LI5, LI6 LI7, LI8	R.F. Coil 9.7-3.6 \| R.F. Coil 4.0-1.5 \| R.F. Coil Broadcast	Mc. 9855 Mc. 9855 9749	R30
	L19, L20	Oscillator Coil 22.3 Mc. Oscillator Coil 180	-17.7 9747	CI
ų	L23, L24	Mc. Oscillator Coil 15.0-	9746	C2
1	L25, L26	Mc. Oscillator Coil 12.( Mc.	9745 )-9.4 9744	C3 C4
	L27, L28	Oscillator Coil 9.7- Mc. Oscillator Coil 4.0	3.6 9743	C5 C6
A STATEMENT	L31, L32	Mc. Oscillator Coil Broa	9742 dcast 9741	C8 C9
	L35, L34	2nd I.F. transformer 2nd I.F. transformer		CII CII CI2
Ì	L37	8 —Loudspeaker field 1100 ohms (Table	287-Z, 8281*	CI4
	L37	Loudspeaker field— 1500 ohms (Cons	ole Model)	C15 C16 C17
	RI	RESISTORS. I megohm, ½ watt	600, 341	C18 C19
ι.	R3 R4 R5	I megohm, ½ watt I megohm, ½ watt I megohm, ½ watt	600, 315 600, 341 600, 341	C21 C21 C22
	R6	600, 507 0.1 megohm, ½ watt	or 600, 707 600, 321	C23
	R8	600, 507 c 16,000 ohms, 2 watt	or 600, 707	C24 C25 C26
		(2 x 32,000 ohms 1 watt in parallel) 600, 511 (	or 600. 711	C27 C28 C29
	R9 RIO RII	1.6 megohms, ½ watt 2.5 megohms, ½ watt 20 ohms 3 watt wire	+ 600, 345 + 600, 349	C30
	R12	wound 20 ohms, 3 watt, wire		C31 C32
	R I 3	II ohms, 3 watt, wire wound		C33 C34 C35
Contraction of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the local distribution of the	R14	20 ohms, 3 watt, wire wound		C36
	R15 R16 R17	0.5 megohms, ½ watt 1.6 megohms, ½ watt 0.5 megohm	600, 335 600, 345	C37
24	••••	control	19006	Clo

rcuit ode No.	Description	Stock Code or Part No.	Circuit Code N	o. Description	Stock Code or Part No.
8	I megohm, I watt 600, 541 or	600, 741	C39 C40	70 uuF silvered mica 110 uuF mica (Table	226, 460
0	20,000 ohms, ½ watt 20,000 ohms, ½ watt	600, 315 600, 307	C40	only) 30. uuE mica (Con	\|32\|\|†
1	0.5 megohm, 1 watt 60 535 or	600 735		sole only)	\|32\|\|†
2	50,000 ohms, ½ watt 50,000 ohms ± watt	600, 315	C41	600v. working	228, 289
	(Console only)	600, 315		only)	13211†
5	250 ohms, 3 watt 50,000 ohms, ½ watt	602, 369 600, 315	C42	30 uuF mica (Con- sole only)	13211+
5	0.4 megohm, ½ watt	600, 333	C43	0.02 uF paper, 600v.
3	0.1 megohm tone	000, 321		only)	228, 307
7	control 0.2 megohm, I watt	19007	C43	0.01 uF paper, 600v. working (Console
) .	600, 527 or 50.000 ohms. I watt	600, 727	C44	only) 50 uuE mice	228, 301
	600, 515 or	600, 715	C45	0.1 uF paper, 400v.	132111
	CAPACITORS.	-	C46	0.1 uF paper, 400v.	228, 121
	52 uuF silvered mica + 2 uuF		C47	working 0.1 uF paper, 400v.	228, 121
	12-430 uuF variable tuning (ganged)	18380	C48	working	228, 121
	200 uuFmica	13211†	C 40	trolytic
	1-25 uuF air trimmer	19659	C49	8 uF, 525 P.V. elec- trolytic
	12 uuF mica	13211†	C50	0.5 uF paper, 400v. working	228, 135
	12 uuF mica	19659	C51	0.005 uF paper, 600v. working	228 295
	1-25 uu⊢ air trimmer 490 uuF mica + 2½%	19659 13212†	C52	0.05 uF paper, 400v.
	2-10 uuF air trimmer 12-430 uuF variable	3658	C53	1500 uuF mica	13213†
_	tuning (ganged) 11-29 uuF air trimmer	18380 3411 B	C55	0.02 uF paper, 600v.	13211†
	42 uuF Temp. Comp. N 2550 uuF mica — 24%	1750 13213†	C55	0.01 uF paper, 600v.	228, 307
	1350 uuF mica ±2½%	13213†	054	only)	228, 301
	11-29 uuF air trimmer	3611 3411 B	C56	25 uF, 40 P.V. elec- trolytic
ļ	50 uuFmica 50 uuFmica	13211†	C57	0.016 uF paper, 600v. working	n de la composition de la comp
:	2 uuF silvered mica + 2 uuF		C57	(Table only) 0.005 µF paper	228, 305
	12-430 uuF variable tuning (ganged)	18380		600v. working	220 205
2	200 uuF mica	13211†	C58	0.5 uF paper, 400v.	220, 275
	I-25 uuF air trimmer	19659		TRANSFORMERS
	-25 uuF air trimmer	19659	TI	Power transformer
Ľ	vorking 2	228, 121		50-60 CPS Power transformer	11344
·	).05 uF paper, 400v. working 2	228, 115	T2	40 CPS Loudspeaker transformer	11346
7	'0 uuF silvered mica 2 '0 uuF silvered mica 2	226, 460 226, 460		(Table only) Loudspeaker transforme	XAI
7	0 uuF silvered mica 2 uuF mica 2	26, 460		(Console only)	TXI
0	0.01 uF paper, 600v.	28 301	C I	SWITCHES.
0	0.1 uF paper, 400v.		31	8 position, rotary	19008
0	0.05 uF paper, 400v.	28, 121	-	Note: Wafers number front of chassis.	red from
7	0 uuF silvered mica 2	228, 115 226, 460	52	Power switch, D.P.S.T. rotary	20007

* Part number of winding only. Some receivers are fitted with I.F. transformers bearing part numbers 8286-Y and 8287-Y. These are wound with solid wire, consequently the D.C. resistance of the windings is higher than when litz wire is used. It should also be noted that when these transformers are fitted capacitor C34 is omitted.

† Capacitance and tolerance (if shown) to be quoted.

Page 6

Page 7

SIMPLE SHORT WAVE CALIBRATION ADJUSTMENT.

The short wave calibration may be adjusted slightly, without removing the chassis from the cabinet for full alignment, by adjusting four cores, L19, L21, L23 and L25 after a station of known frequency is received.

The correct procedure is as follows:----

(1) Set the dial pointer so that calibration is correct on the medium wave band.
(2) To adjust the calibration of the 22.3-17.7 Mc. band, tune in the known station, and to shift the pointer position to the left, turn L19 clockwise or vice-versa until the station can be tuned in at its assigned frequency.
(3) The adjustments for the 19.0-15.0, 15.0-11.7 and 12.0-9.4 Mc. bands are similar, using L21, L23, and L25 respectively.

Align- ment Order.	Test Ins. Connect to Receiver.	Frequency Setting.	Band Setting.	Calibration Scale Setting.	Circuit to Adjust.	Adjustment Symbol.	Adjust to Obtain.
1	6J8G Cap.*	455 kc.	Broadcast	0°	2nd I.F. Trans.	Core 136	Max Peak	SEC
2	6J8G Cap.*	455 kc.	Broadcast	0°	2nd I.F. Trans.	Core L35	Max. Peak	Da ,
3	6J8G Cap.*	455 kc.	Broadcast	0°	Ist I.F. Trans.	Core L34	Max. Peak	850
4	6J8G Cap.*	455 kc.	Broadcast	0°	lst I.F. Trans.	Core L33	Max. Peak	SEC
			Re-check I, 2	, 3, and 4.				PRI
5	Aerial	600 kc.	Broadcast	19°	Oscillator†	Core L31	Calibration
6	Aerial	1500 kc.	Broadcast	- 168°	Oscillator	C14	Calibration
7	Aerial	1450 kc.	Broadcast	158°	Radio Frequency	C28	Max. Peak	1
8 -	Aerial	1450 kc.	Broadcast	158°	Aerial	C10	Max. Peak	1
	•		Re-check 5, 6	7, and 8
9	Aerial	17.8 Mc.	22.3-17.7 Mc.	18°	Oscillator	Core LI9	Calibration 7	BON.
10	Aerial	1 7.8 M c.	22.3-17.7 Mc. 🎽	18°	Radio Frequency†	C26	Max. Peak	7
· 11	Aerial	17.8 Mc.	22.3-17.7 Mc.	18°	Aerial	C8	Max. Peak	7
12	Aerial	21.0 Mc.	22.3-17.7 Mc.	149°	Oscillator	C12	Calibration
13	• Aerial	15.2 Mc.	19.0-15.0 Mc.	27°	Oscillator	Core L21	Calibration	6
14	Aerial	11.8 Mc.	≰ 15.0-11.7 Mc.	25°	Oscillator	Core L23	Calibration	5
15	Aerial	11.8 Mc.	15.0-11.7 Mc.	25°	Radio Frequency†	C25	Max. Peak •	5
16	Aerial	11.8° Mc.	15.0-11.7 Mc.	25°	Aerial	C6	Max. Peak	5
17	Aerial	9.5 Mc.	12.0-9.4 Mc.	24° ·	Oscillator	Core L25	Calibration	4
18	Aerial	9.0 Mc.	9.7-3.6 Mc.	156°	Oscillator	C18	Calibration	3
19	Aerial	9.0 Mc.	9.7-3.6 Mc.	156°	Radio Frequency†	C27	Max. Peak	3
20	Aerial	9.0 Mc.	9.7-3.6 Mc.	156°	Aerial	C5	Max. Peak	3
21	Aerial	4.0 Mc.	9.7-3.6 Mc.	19°	Oscillator	Core L27	Calibration	3
			Re-check 18,	19, 20 & 21
22	Aerial	1.6 Mc.	≉ 4.0-1.5 Mc.	15°	Oscillator	Core L29	Calibration	2
23	Aerial	3.7 Mc.	4.0-1.5 Mc.	153°	Oscillator	CI9	Max. Peak	2
Re-check 22 and 23

ALIGNMENT TABLE.

Finally, re-check broadcast band. This is necessary only if the setting of C12 has been altered.

† Rock the tuning control back and forth through the signal

* With grid clip connected. A 0.001 uF capacitor should be connected in series with the "high" side of the test instrument.

The column headed "Calibration Scale Setting" refers to the 180° scale on the ganged tuning capacitor drive drum. In taking readings on this scale, read from the right-hand edge of the pointer, that is, the edge nearest the rear of the chassis. Check the setting of the drum before taking readings. The zero mark should be opposite the pointer with the tuning capacitor fully closed.

CHASSIS REMOVAL AND REPLACEMENT.

Turn the Phono-Range Switch to the 22.3-17.7 Mc. position and then remove the three control knobs from the front of the cabinet. These knobs are each held by one set screw.

To remove the two knobs at the side of the cabinet, proceed as follows:---

Table Model:

The knobs pull straight off. Do not loosen the set screw in the lower knob. If difficulty is experienced in removing this knob, refer to the label adhered to the inside of the cabinet for instructions.

Console Model:

The knobs are not removed but the spindles to which they are attached are parted at the couplings within the cabinet.

(2) Disconnect the dial pointer from the drive cord, first unscrewing the thumb nut, and disconnect the cable from the loudspeaker.

(3) Disconnect the Bowden cable which actuates the band indicator on the dial scale. The cable is connected to the dial assembly at two points, the sheath to the top left-hand corner of the dial assembly (viewed from the rear) and the core to the band indicator. Loosen the thumb screws at these points and carefully free the cable from the assembly.
(4) The chassis is held in the cabinet by four bolts. Remove these and withdraw the chassis from the cabinet.
(5) Replacing the chassis in the cabinet is a direct reversal of the above instructions, but care must be taken to connect the dial pointer to the drive cord as follows:—
- (a) Turn the tuning control to bring the ganged capacitor plates into full mesh.
- (b) Connect the dial pointer to the drive cord with the pointer in a position opposite the setting mark on the dial scale, which is approximately 5/16 inch to the right of the 550 kc, calibration point

Page 8

CONNECTION TO POWER SUPPLY.

The receiver should not be connected to any circuit supplying other than alternating current from 200 to 260 volts and at the frequency stated on the label within the cabinet. The power supply connection panel is shown in the accompanying diagram, and for 230 to 260 volt operation the input leads from the power switch (S2) should be connected to tags B and G. For operation on voltages below 230, connection should be made to tags B and W.

"SERVICE WINDOW."

A "Service Window" is provided in the base of the table model cabinet. The "window" is normally covered with a perforated grille fastened by four knurled nuts. With the grille removed, it is possible to perform most service operations without removing the chassis from the cabinet.

TUNING DRIVE CORD REPLACEMENT.

The accompanying diagram shows the route of the cord and the method of attachment. Whilst fitting the cord, keep it taut and adjust the length so that the tension

DESCRIPTION OF TUNING CIRCUIT ADJUSTMENTS

BROADCAST BAND.

The broadcast band adjustments follows usual practice with three trimming capacitors—C10 aerial, C28 R.F., C14 oscillator and a variable magnetite core for L.F. adjustment of the oscillator coil L31, L32.

9.7-3.6 Mc. BAND.

Adjustments are the same as those used on the broadcast band, that is, with three trimming capacitors—C5 aerial, C27 R.F., C18 oscillator and a variable magnetite core for L.F. adjustment of the oscillator coil L27, L28.

4.0-1.5 Mc. BAND.

All capacitors in the aerial and R.F. sections are common with those in the 9.7-3.6 Mc. band, the change of band being accomplished by switching tapped coils. The oscillator section, however, is provided with a separate capacitor, C19, for tracking with the signal circuits at the H.F. end and a variable magnetite core for L.F. adjustment of the oscillator coil L29, L30.

22.3-17.7 Mc. BAND.

At the L.F. end of this band there are three adjustments, a magnetite core in the oscillator coil L19, L20 and trimming capacitors C26 R.F. and C8 aerial. Small capacitors, C1, C22 and C15, are used in series with the ganged tuning capacitors to accomplish band-spreading at the L.F. end of this band. The oscillator circuit is made to track with the signal circuit at the H.F. end by adjustment of capacitor

spring measures approximately 2 inches long when fitted. The spring should be sheathed to prevent it from rattling against the drum.

LOUDSPEAKER SERVICE.

It is inadvisable to attempt loudspeaker repairs other than adjustment of the voice coil and replacement of the transformer. The fitting of a new cone or the replacement ment of a field winding should be done only by Service Departments suitably equipped to do the work.

To centre the voice coil, first remove the dust cover. To do this, use a sharp razor blade and cut the centre out of the dust cover, cutting just inside the edge of the voice coil former, which can be felt with the forefinger. Do not attempt to tear the cover from the cone. Loosen the suspension screws, insert three narrow paper "feelers" in the gap and re-tighten the suspension screws. The "feelers" should be approximately 3-16 inch wide and 0.006 inch thick.

After adjusting, test the loudspeaker, and, if satisfactory, fasten a replacament dust-cover in place with latex rubber cement. See "Mechanical Replacement Parts."

C12. The three series capacitors are chosen to give three point tracking between the signal and oscillator circuits.

19.0-15.0 Mc. BAND.

The capacity system is the same as for the 22.3-17.7 Mc. band, the change of band being accomplished by switching coils, the oscillator coil L21, L22 being fitted with a variable magnetite core for L.F. adjustment.

15.0-11.7 Mc. BAND.

Adjustments are similar to those on the 22.3-17.7 Mc. band, excepting that no H.F. adjustment is provided for the oscillator. L.F. adjustments are trimming capacitors C25 R.F. and C6 aerial and a variable magnetite core in oscillator coil L23, L24.

12.0-9.4 Mc. BAND.

One adjustment only is provided, a variable magnetite core in the oscillator core L25, L26.

It will be noted that the ratio max. frequency min. frequency

is the same on the four bands, 12.0-9.4 Mc., 15.0-11.7 Mc., 19.0-15.0 Mc., 22.3-17.7 Mc., and the tracking is practically

r correct, using the same series capacitor for all bands. The ratio max. frequency is also the same on the 4.0-1.5 Mc. and

9.7-3.6. Mc. bands, but, due to the greatly different frequency spectrum of the oscillator, the series capacitors in the two oscillator circuits are different.

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CIRCUIT DIAGRAM

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CHASSIS (Underneath View).

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CIRCUIT DIAGRAM