Fig. 5.-Tuning Circuit Arrangement.
MEDIUM WAVE BAND. The Medium Wave band adjustments follow usual practice with mee trimming condensers—Cr Aerial. C22 R.F., C? Oscillator and a variable coil adjustment L31 at the L.F. end in the oscillator section.
Adjustment arrangements are the same as those used on the Medium Wave band, that is, with three trimmers—C6 Aerial, C21 and C13 Oscillator and L.F. Oscillator coil adjustment L27.
All the condensers in the aerial and R.F. sections are common with those in the 31-83 M. band, the change of band being accomplished merely by switching tapped coils. The oscillator section, however, is provided with a separate condenser, C14, for tracking with the signal circuits at the H.F. end and a core adjustment, L29, for tracking at the L.F. end.
At the L.F. end of this band three adjustments L19 oscillator, C19 R.F. and C2 aerial. Small series condensers C1, C50 and C8 are used in series with the tuning condenser sections to accomplish band-spreading at the L.F. end of this band, the oscillator circuit is made to track with the signal circuits at the H.F.
end by a ljustment of CIL. The three series condensers mentioned above are chosen to give three point tracking between signal and oscillator, circuits.
The capacity system is exactly the same as for the 13-16 M. band, the change of band being accomplished merely by switching coils, the oscillator of which is variable (L21) for the adjustment at the L.F. end of the band.
Adjustments are similar to those on the 13-16 M. band except that there is no H.F. adjustment for the oscillator. Adjustments at L.F. end are trimmers C20 and C3 and core L23.
Only one adjustment (L25) as on the 19 M. Band. It will be noticed that the ratio, max. frequency is the same on
It will be noticed that the ratio, min. frequency the four bands, 31 M., 25 M., 19 M., 13-16 M. and the tracking is practically correct using the same series condenser for all four bands. The ratio, max frequency is also the same on the 75-200 M. and 31 83 M. bands, but due to the greatly different frequency spectrum of the oscillator, the series condensers in the two oscillator-circuits are different.
Models 701, 702, 276 and 316
SIX VALVE, SEVEN BAND, A.C. OPERATED SUPERHETERODYNES
Technical Information & Service Data
The Radiola Models 701, 702, 276 and 316 are six valve, A.C. operated superheterodynes with a tuning range of 22.5 M.C. (13.3 M.) to 550 K.C. (545 M.) in seven bands. Bandspreading is provided on the 16, 19, 25 and 31 metre bands and ease of tura, ing on these bands is comparative with that on Medium Wave broadcasting.
The design of the R.F. Switch and Coil Unit is unique and the high performance of the instrument is largely due to this component. Built and tested as a self-contained unit, it may be readily removed from the chassis for servicing, if necessary.
Other features of these Models include the following: Permeability tuned escillator coils and I.F. transformers: temperature compensated circuits: straight line frequency tuning condenser; illuminated band indicator on dial; "Beam-Power" output stage; inverse feed-back; dustproof welded-construction elecro-dynamic loudspeaker.
On all models the dial with the dial pointer attached is a separate mounted on the cabinet. The drive cord connects to the or upon fitting the chassis in the cabinet.
OTNITER MODEL 701.
Standard table model for 200-260 V. operation. Fitted with flatglass edge-lit dial scale inclined on top of cabinet and 7in. loudspeaker mounted on the chassis.
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, Types J6726 and C1070.* An output motor is necessary with both these instruments.
As the calibration of the band-spread bands (16, 19, 25 and 31 M.) requires great accuracy, it is recommended that an A W.A. Crystal Calibrator, Type 6795 be used, after setting C escillator calibration, to check the accuracy of the Signal revels of either 100 or 1000 K.C. throughout the radio frequency inverses of either 100 or 1000 K.C. throughout the radio frequency s, ectrum, 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 K.C. position a spurious image signal can generally be tobtained by turning the tuning control of the Receiver to a poirt approx. 100 K.C. higher in frequency. This is a useful check as to whether a harmonic or a spurious image is being tuned. If a Cr,stal Calibrator is not available, broadcasting stations of known frequency may be used as an alternative.
When using a Signal Generators or Modulated Oscillator with the tuning of the Receiver fixed, two frequencies can be tuned
Export table model litted with a universal power transformer for 95-250 V. operation, special export glass dial scale power switch in volume control, and with components specially impregnated to suit tropical conditions. Apart from the above details, the chassis employed is identical with that used in the Model 701.
The Console equivalent of Model 701. Fitted with visual Tuning Indicator, Convex Quadrant dial and 12in. loudspeaker detached from the chassis. The power transformer used differs from that installed in the Model 701 chassis in that the secondary voltage rating is higher to suit the loudspeaker field coil.
A Radio-Gramophone combination employing the same chassis as that used in the Model 276 plus a suitable phono. pick-up filter circuit and Radio-Phono. Switch. A Tuning Indicator is not fitted. The gramophone motor used is a "Garrard" A.C. induction type with an automatic stop davice.
from the test instrument, one .92 M.C. 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.
Perform alignment in the proper order as shown in the chart, starting from No. 1 and following all operations across, then No. 2, etc.: Adjustment locations are shown in figure 1 and in the layout diagrams.
Keep the Volume Control set in the maximum clockwise position and regulate the output of the test intrument 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 satisfactory aligned, seal the adjusting screws with a small quantity of celluloid cement to eliminate the possibility of their shifting.
* If a Type J6726 or C1070 instrument is used, see that a 250,000 ohms resistor is connected between the output terminals and for Short Wave alignment, a 400 ohms non-inductive resistor in series with the active output lead.
The Short Wasa 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 whose froguency is definitely known is received.
The correct procedure is as follows:----
Fig. 1,-R.F. Adjust Location
Align
ment Orde |
Test Inst.
Connection r. to Receiver. |
Test Inst.
Frequency Setting. |
Receiver
Band Calibration Sotting. Scale Setting. |
Circuit
to Adjust. |
Adjustment
Symbol. |
Adjustment.
Type. Core |
Adjust fo
Obtain |
---|---|---|---|---|---|---|---|
*6.18G Grid Cap | 455 K.C. | Meg. Wave 0 | 2nd I.P. Trans. | 135 | Core | ||
*6J8G Grid Cap | 455 K.C. | Med. Wave | 2nd I.F. Trues | L34 | Core | ||
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ז. |
*6J8G Grid Cap | 455 K.C. | Med. Wate | Ist LE Trans | L33 | Core | Max. (Pear) |
4 | *6J8G Grid Cap | 455 K.C. | Med. Wave U | Oscillator | - L3 I | Core Core | Man (Peak) |
5. | Aerial | 600 K.C. | Med. Wave 17.3 T | Oscillator | C9 | Air. Trim. | Max. (Peak) |
6 | . Aerial | 1500 K.C. | Med. Wave 105. | R.F. | C22 | Mica Trim. | Man Tool |
. 7 | . Aerial | 1:30 K.C. | Med. Wave 101.5 | Aerial | C7 | Mica Trim. | Max. [Peak] |
Ŷ | Aerial | 17.8 M.C. |
Re-check adjustmen
13-16 M. 14.5° 13-16 M. 14.5° |
t 5, 6, 7, 8.
Oscillator R.F. |
L19
C19 |
Core
Mice Trim. |
Calibration
Max. (Peak) |
10 | Aerial | 17.8 M.C. | 13-16 M. 14.5° | Aerial | Ç Ç 2 | Mica Trime | 1747, [ 444] |
Aerial | 13.16 M. 150*+ | Oscillator | CII | Air, Him, | Calineation2 | ||
12 | Aerial | 19 M. 18° | Oscillator | Ļ21 | Core | Calibration | |
Aerial | ILS MC | 25 M. 22° | Oscillator | L23 | Core | LAN Peak | |
4 Aeriai | 11.8 M.C. | 25 M. 22°. | R.F. | C20 | . Mica Irima | Mon (Deal) | |
> II | 5. Aeriai | I & MC | 25 M. 22° | Aerial | C3 | Mica Irim. | Calibration1 |
6. Aerial | A M C | 31 M. 26° | Oscillator | L25 | Core | Calibration | |
ł | 7. Aerial | 95 M.C. | 31-83 M. 169° | Oscillator | C13 | Air. Irim. | Max (Peak) |
8. Aerial | 65 M.C. | 31-83 M. 169° | R.F. | C21 | Mica Trim. | Max. (Peak) | |
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95 M.C. | 31-83 M. 169° | Aerial | C6 | MICO ITIM | Max (Peak) | |
2 - Z | 4 M.C. | 31-83 M. 18°† | Oscillator | L2/ | |||
2
₹ |
I. Aeriai | Re-check adjustme | nt * 18, 19, 20. | Cara | Mar (Peak) | ||
a Aorial | 1.5 M.C. | 75-200 M. 3°† | Oscillator | L29 | Ata Taim | Max. (Peak) | |
2 | 2. Aorial | 3.8 M.C. | 75-200 M. 175°† | Oscillator | C14 | ||
2 | 2. Aanai |
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tmant 22 | 1.28 | 結果ない。 |
Finally, re-check Medium Wave band. This is only necessary if the setting of CII (21.4 M.C.) has been altered *With grid clip connected. A .001 mfd condenser should be connected in series with the active output lead of the test instrument. +Rock the Tuning Control back and farth through the signal.
$An alternative method of making this adjustment is to rock the tuning control for mox. peak. The calibration may ly out.
The column headed "Receiver Calibration Scale Setting" refers to the 1887 scale on the tuning condenser drive drum. readings on this scale read from the right-hand edge of the pointer; that is the edge nearest the rear of the chassis. Check s drum before taking readings. The zero mark should be exactly opposite the pointer with the tuning condenser plates in full mesh. In taking Check setting of
Carla | Daut | CII | 3658 2-10 mmfd Ale Trimmer | |
---|---|---|---|---|
Code. Part
No. No. COILS. |
Loae. | No RESISTORS. | C12 | 9596A Tuning Condenser (1) |
10 10 9748 April Coil 1500-550 Kr | NO. | I meg. 1/3 watt | C13 | 3661 2-20 mmfd Air |
L9, 19 9748 Aerial Coll 75 200 M | ~R? | 50.000 ohms 1/3 watt | C14 | 3411 11-29 mmfd Al |
(10,7,0 9054 Aerial Coll 21,92 M |
100.000 chms 1/3 watt
|
C15
|
2550 muld MR
|
|
10,7 9054 Aeriai Coli 51-05 W. | _R4 | 20,000 ohms 1 watt | C16 | 1350 mmfd Mid |
L1, Z, 3 (9852 Aerial Coll 31 M. | -R5 | 50.000 ohms 1/3 watt | · C17 | 200 mmfd Silvered Mica |
R6 | 9484 500,000 -chms Vol. Control | C18 | 50 mmfd Silvered Mica | |
1 2 3 9852 Aerial Coil 19 M | ~R7 | 1.75 meg. 1/3 watt | C19 | 3-30 mmfd Mica Trimmer |
-R8 | 1.75 meg. 1/3 watt | C20 | 3-30 mmfd Mica Trimmer | |
L1, 2 9852 Aerial Con 15-16 M. | R¶ and a | 20,000 ohms 2 watt | C21 | 3-30 mmfd Mice Trimmer |
L17, 18 9749 R.F. Coll 1500-550 Rc. | ~R10 | 15,000 ohms 1 watt | C22 | 3-30 mmfd Mica Trimmer |
L15, 16 9855 R.F. Coil 75-200 M. | RII | 20 ohms 3 watt | C23 | 9596A Tuning Condensar |
L15 9855 R.F. Coil 31-83 M. | _R12 | 20 ohms 3 watt | C24 | 70 mmfd Silvered Mice |
L11, 12 19853 R.F. Coil 31 M. | 4-R13 | 2.3 meg. 1/3 watt | C25 | .) mfd Paper |
L13, 14 ) | ⇒R14 * | 11 ohms 3 watt | C26 | 70 mmfd Silvered Mise |
L11, 12, 13 9853 R.F. Coil 25 M. | -R15 | 20 ohms 3 watt | C27 | 70 mmfd Silvered Mice |
L11, 12 9823 R.F. Coil 19 M. | -R16 | 500,000 ohma 1/3 watt | C28 | ,01 mfd Paper |
131 9853 R.F. Coll 14-16 M. | R17 | 1.5 mag. 1 walt | (.29 | ,I mid l'aper |
-1118 | 200,000 ohms 1 watt | C30 | .05 mfd Paper | |
L31, 32 9741 Oscillator Coll 1900-550 Kc. | -R19 | # 3 meg. 1 walt | C31 | 4 mmfd Mica |
1.29,30 9742 Oscillator Coil 75-200 M. | -R20 | 50,000 ohms 1/3 watt | C32 | 70 mmfd Silvered Mice |
L27, 28 9743 Oscillator Coil 31-83 M. | -R21 | 200 ohms 3 watt | C33 | 70 mmfd Silvered Mich |
L25, 26 9744 Oscillator Coil 31 M. | -R22 | 50,000 ohms 1/3 watt | C34 | 30 mmfd Mica (U) (C'sole) |
123 24 9745 Oppillator Coil 25 M | R23 | 9765 100,000 ohms Tone Control | C34 | 110 mmfd Mica (L) (Table) |
R24 | 50,000 ohms 1 watt | C35 | 30 mmfd Mica (U) (C'sole) | |
L21, 22 9746 Oscillator Coil 19 M. | 2 R25 | 1 meg. 1/3 watt | C33 | 110 mmfd Mica (L) (Table) |
L19, 20 9747 Oscillator Coil 13-16 M. | • _R26 | lineg. | watt | C36 | .02 mfd Paper |
L33, 34 8286 1st I.F. Transformer | R27 | 20,000 ohms 1 watt | C37 | .1 mfd Paper |
1.35.36 8287 2nd LF. Transformer | -R28 | 1.75 meg. 1/3 watt | C38 | 16 mfd., 525 V. Electro. |
- R29 | 1 meg. 1 watt 3 | C39 | 50 mmfd Mica (D) | |
(Console) 1500 onms held | R30 | 50,000 Šhais 1/3 watt | C40 | 200 mmfd Mica (J) |
L37 (Table) 1100 ohms field | (Console only) | C4 | .02 mfd Paper | |
Code | Part | C42 | .1 mfd Paper | |
TRANSFORMERS. | No. | No. CONDENSERS. | C43 🔾 | .5 mfd Paper |
TI (Table) 70796 ) Power Transformer | - 1 ( C I ) ( 1 ) | 31 mild Bilvered Mise | C44 | .1 mfd Paper |
11 (Concole) 844413 | 30.60 c. | C2 | 5.50 minfd Mica Trimmer | C45 | 16 mfd., 350 Reg. Electro. |
TI (Table) 2081(C) Power Transformer | C3 | 5-50 minted Mica Trinmer | C46 | 25 mfd., 25 V. Electro. |
T1 (Console) 8446B1 40 c. | C4 | 200 mm/d Silvered Mice | C47 | .1 mfd Paper |
TI 0737 A Power Transformer | C6 | 5.50 mmfd Mica Trimmer | C48 | .0025 mfd Paper (Console) |
Export | C7 | -50 mmfd Mica Trimmer | C48 | .015 mfd Paper (Table) |
T? (Table) XAI Loudeneaker Trans- | C8 | 40 mmfd Temp. Compen- | C49 | 200 mmfd Silvered Mica |
former | sated | C50 | 53 mmfd Silvered Mica | |
T2 (Console) TX20 Loudspeaker Trans- | C9 | 3411 11-29 mmfd Air Trimmer | C51 | .05 mfd. Paper |
former | C10 | 490 mmfd Mica Padder | C52 | .05 mfd. Paper |
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