Decca fs service manual

Page 1

Electrical and Radio Trading, January .1969

DECCA r
s c1 1
c2 1
2: :1
SERVICE c. 1.
STE REG 26 l
7
CHART cs 3
c9 s
cm 3
1573 RADIOG RAM v
(:11 2l
C13 9.
:14 ex
C15 3.
C16 4.
C17 H
e a: 2,:
. Additional copies of this chart Is 611..
In teak h 1, th I s: . . , cm 3.
aisle. :....?'.::§:?:: mcludme postage. mm, w g; 3;
MW and LW aerizls and direction orderplemw ERT, 33-39190Wmg w 3_
control' at the treble units to match room Green Lane. London EC1. C24 g:
characteristics :25 ga
82 z:
OUR waveband radio tunes LW. common IF amplifier AFllG, TR6A/ Wavebands. SW 51-17m(5.85-18.3mc,ls), C13 35
MW, sw and VHF/FM bands and has TRGB gram equaliser and pre-amplifier MW 576-182m (520-1620kc/s), LW 83 3;
socket for stereo decoder. Stereo trans- LH/RH channel SFT237, TR7A/TR7B 2069-1112m (145»270kc/s), VHF/FM C31 10
cription head plays through three speakers AF amplifier LH/RH channel SFT353, 88-100.5mc/s. C31 0
per channel, housed in lined reflex TR8A/TR8B AF amplifier LH/RH chan- ms. AM 472kc/S,FM Hume/s. 833 :
enclosures and delivering 5W per channel nelOC44, TR9A/TR9B AF driver LH/RH Aerials. Internal aerials for MW LW C35 3.
output, channel OC81, TRlOA/TRIOB AF output and VHF/FM. Aerial directional control 8; 1"
Mains. 200-250V AC. LH/RH channel AD140. for MW and LW.
Consumption. 245mA. Diodes. Dl FM clamp diode OA90. Pilot lamps. Speaker and dial lamps,
Transistors. TR] FM RF amplifier D2 FM/AM clamp diode OA79, D3 FM feur 6.5V. 03A. MES type.
AF178, TR2 FM mixer/oscillator AFIIS, AGC diode _OA91, D4 and D5 FM dis» Inputs. Sockets for stereo decoder and
TR3 FM IF amplifier/AM mixer AFllS, crimmator dlodes OA79, D6 AM detector tape recorder stereo playback. External
TR4 common IF amplifier AF116, TRS diode OA90. AM aerial socket.
5 1 I! I4 IS )4 l9 2! Z)
l l 2 s 4 s a y lo ll I2 I? la" 29 22 24
c 2 manila '5 :gglm 2v 2.227 w as 29 u :23 22 5* zzss 5: 22 2: 2?
r ' H 4 . ° . EH: 3 i:
M unn- _ _ _ _
l-____vv" _____ 17g- _________________
561

SEAN

M IFY

Diagram of RF and IF circuits. Voltages positive with respect to different to LW and MW. Readings taken withiD,Mohm/volt meter under no signal conditions

Page 2

Vintage Service Data CD-Ftom

APACITORS C33 41597 c1 C77 11» c1 | I j I
I 15hr E2 C39 3-30pF C1 C73 10KpF 51
1 IOKpF E1 C40 zs1pI= C1
3 35pF 51 C41 3-30pF c1 -
4 KpF 51 C41 7 c1 RESISTORS r1 r2
5 IDKpF 21 C43 SKpF 7 R1 330 E1.
s 15,; £1 C44 121 R1 1K E2 -
7 ZKpF E2 C45 500ka C1 R3 81 E1 | -
a 4.5.1opF E1 C46 1DmF 31 R4 560 E1 :| 2
9 5.6pF El C47 1K F c1 R5 6K8 E1
to 390p: El C49 100KpF C1 R6 "(5 E1
11 10KpF E1 C49 _ c1 R7 17K c1
11 ZKpF E1 cso - 51 Re 3K9 C1 "2 L2.
13 6.1pF E1 CS1 31 R9 1K (:2
14 sapr E1 cs1 3KpF :1 R10 1K C2
15 8.2pF 21 C53 C1 R11 47 C2
I6 45-10» 21 C54 leF 32 R11 1K 52 -
I7 190pF £1 :55 1mI= C1 R13 3K9 s1 5
18 1va El cs7 SflDmF (:1 R14 can sz
[9 sapF C1 :5: 1KpF c1 R15 56K c2 7,,
to 3-30pF C1 cs9 89F Bl R16 3K9 c1
11 3-309F c1 cs0 -- 31 R17 4K7 52
11 zapr c1 cs1 c1 R15 110 (:1 t
g 3-30pF c1 22% IOOmF Ei R19 210 C2
gang c3 _ R10 470 c1
15 gang c3 :64 soomr c1 R11 18K 82 :7 E
16 gang C3 C65 100pF Bl R11 5K6 c1 _4 -aa _35
ii 30" 2% 52? WE E1 3 °° 3
KpF p 1 R14 470 CI
19 3K9pF :1 C68 1K5pF c1 R15 3K3 BI 14
so IDOKpF C1 C99 IOKpF :1 R26 330 B1 zi 59 E 21 I,
31 \OmF 31 C70 10KpF C1 R17 390 CI $1 0" @ H 54 5 012]
31 lOKpF 31 C71 ISmF 31 R19 39K C1 :5 u 25"] [ll l@- R
33 -. C2 C71 2mF :1 R20 1R1 c1 25
34 - c1 c7: ImF c1 R31 4K7 c1 ~- Elm um 43 lo 1-.
35 nape c1 C71 500pr 51 R31 4K7 C1 El :27 pm I]? 2 -
as 3K6pF C1 C75 IKoF (:1 R33 47K 82 I Tu Elsi]
37 gang c3 C76 10%» 31 R34 1K5 82 W
£7 3-D 66 3
Outlets. Provision for external speakers I] U m
of 150hm impedance. Five- -pin tape 55 5" ~
-za ®
recorder socket for stereo recording and El '9
playback. 11 ® J-L]
, r ~ A
m Uifli Li ' 9
lg ll ll ll
_23-T_
24 at 27 :1 so 29 n
as w a 5570 as 517, 7| 72 7 p _
59 0| {,1 so 75 Above, component layout: on IF board and power chassis; above m
l7 Is 16
fl " _ W - - *_ - - _] Fuses. F1, F2 2A. output meter, dummy aerial, IOKPF
Output. 5W perchannel. capacitor, trimming tools, polystyrene
Speakers. Each channel has leéin. cement.

hIgh flux bass unit of 150hm impedance
in lined reflex enclosure and two 4in.
round treble units of Sohm impedance.

General. Connect output meter across
secondary terminals of one output

123

' Cr 55 k h oint transformer. With ganged capacitors
i26 5" l (g/sever networ S ave crossover p fully closed and FM tuning drum turned
i Record unit. Garrard AT6 Mk. 11 fully clockwise, check that» tuning pointer
Iiwlc'non four-speed autochanger with provision Is located under datum lInc at low fre-
i for manual control, quence end of tunIng scale. Turn volume
i Pickup. Deram Stereo Transcription and tone Controls to maximum~ and
head fitted with high compliance stylus adJusl ,suznal generator to maintain
i suitable for mono and stereo records. apptoXImater 500mW OUIPU throughout
m_ m IFT Stylus. Deram Diamond/S, coding Blue, alignment
lus force. 4-5 rammes. .

I" 0'6 "127%! Sty g - AM IF. Swttch to MW and fully mesh
| l7 m 59 5. i Tervaélggflurer' Decca Radio and gang Disconnect lead to MW aerial coil
5: l - ' tap and connect Slgnal generator vta
i EL, QlizlnggwDapgglmelnvgndgrnggag PEPE? lOKpF capacltor between free end of
L _ _ .l i 01-622 6677 lead and fixing screw for gang condenser
1 to which IF board earth is connected.
Inject 472kc/s signal modulated 30 per
59 s :5 SERVICE NOTES cent to 400c/s. Adjust input level to give
Tuner. TR] and TRZ are both connec- not more than 500mW output. Adjust
mom i ted in grounded base configuration and cores of T7, T5 and T2, in this sequence,
70 located in separate FM tuner unit. TRl to obtain maximum output, Check
:- i is RF amplifier with AGC, TRZ is sclf~ centre frequency and symmetry, readjust

[ oscillating mixer. if needed. Reconnect aerial leadt

If baseemitter short occurs in either,

D, 52 4 i then the base or emitter potential with FM 1F SWIICh 0 FM and {NW 18511
-- :' I respect to earth will equal full supply gang COMIC Signal generator V13
24 voltage A base-emitter open circuit in lOKRF came-tor 0 emitter 0f TR3 and
| either stage will cause emitter potential 91135515 earth 95 above. Inject 107mC/S at
to equal supply voltage. Z_5kc/s devtatton, adjusting Input level to
i If either TRl or TRZ is replaced, slight give "0 more than 500mW output
f + V RF adjustment may be needed. If for any Adjust m turn cores 0f T5 T4 and T3 10
{WSK I other reason the FM tuner unit is thought g maXImum output Check centre
1 to be faulty, remove complete gang frequency 311d symmetry and readjust 1f
condenser and tuner unit assembly and 93?5,53ry. Swrtch generator t9. AM
-- - fie « - _ -- ~- A - relurntoDeccaservicedepartment, vosmon and adJust R18 for minimum

N, third figure on SW where

ALIGNMENT
Equipment required. AM/FM signal
generator covering 10kc/s to 100mc/s,

www. vin tage-radio. com

output.

FM RF. Tune receiver to 88mc/s.
Inject 88mc/s signal at 25kc/s deviation to
FM aerial and earth socket, adjusting