Decca 110 120 service manual

Page 1

I (Supplement)

TRADER

SERVICE SHEET

280

THE WIRELESS & ELECTRICAL TRADER

D ECC

January 8, 1938

A99.

lIO AND I20

COMPONENTS AND VALUES

.

HURT-\«VA \l-: ranges of 12-35 double (liude valve (V4, Mullard metallised
(referred to below as S.V\.i) and 2D4A). Audio frequency component in
35400 in. (S.W.z) are covered by the rectified output is developed across load RliSlSlANCFS (Vim;
Decca 0) 5-\'al\'0 (plus rectifier) All resistance BIG and fed via Ll. stopper 7 ° "5
4Jiaml superhet. The receiver is suitable R15, switch 829, .l\.[-l coupling condenser Rx r, 500.000
for mains of lvi5- 55 V, 50-60 C/S, and 024 and manual volume control R20 2 " 3°"
has prm siou for 0th a gramopllonc to CG. 1)! pcniode output valve (V5, iii .lemupliiii; :: 35,me
pickvnp and an extension speaker. Mazda A04/Pen).' Fixed tone correction R5 stubillscr .l 50
.\n identical chassis is fitted in the by C26 and variable tone control by R" LR? "5'20
[[0 radiogranl and the 120 automatic 027 and R24 in anode circuit. Provision E; 505,12:
ladiugram, but this Sandra Sheet was for connection of high impedance external R1) A 41
prepared on a ()9 table model. speaker acr 5 primary of T1. :3? m do HT Iced 30 31
CIRCUIT DESCRIPTION For gramoplm'ne operation Y3 is used qu (;,~,...H{ici?lnpgfi_ui.t 50:000
Aerial input via coupling coils L1 as} an A}, amplifier: Connection [or the 3:3 :1); hxcthLreilslancc 1:
(SANA), L2 (S,\V,2), L3 (M.W.) and pickup is piovrderl lntlle ionn of a pair Rig H H Mom,
L4 (l.,W.) to singletuned circuits L5, of sockets 1 the grid Circuit of V3: R, V. gnaldiodcloml r. . swam
035 (SWVJ), L3, 035 (551, L7, 085 (when tile control su'itch IS tnrneddu iilfl iVrA .dlnde loud rcflsi 3%,m
[l\l.W.) and L8, 035 (L.\V.), which "Fa, Posm" 329 019 ,"thii nit, l\.V"'."mli...-amnilnli..g" 0:000
precedevariable-mupentorleR,F,amplifier "m l 330 €105? 9"""e°l~ VB 1" Mill-3"[l-I'|m"l"? 5 W
(V1, Mallard metallised VP). anode to the grid circuit {if Y6 Via E2: P5 (.13. and AWL (Lflyj it);
Tuned-secondary transformer couplingr re an: capaclty coupling rm": 00" kg; .. 150
by L9. L13, 0443 (awn, L10. L14, 040 Mg RM 094 3 320- in. wow:
{SM/.1), L11, L15, U40 (M.W.) and Smond (limle of V4, led from tapping
L12, L16, C40 (I..W) between V1 and mi L28 via 023, provides I) C potentials
and. licxodc valve (v2, Mazda metallised which are developed av" .4 load my v5.1"...5
AC/THI or Mullard TH4A) which operates sistauucs R17, R18 and (oil I): k through in
as frequency changer with internal (ICCOIPHHH circuits as Q- m R 11, VCI V ;@,5
coupling, lrlmlennmlc coils L21(S.\V.l), 111 and H- valves, giving nntmnatic L2 m '
L22 (S,\\,z), L23 (MAM) and L24 (l..WV) volume control. :33 .. g;
urn tnnorl by (:47; parallel trimming by H.l. current i. sunlled by l.ll.('. 1' . . 5 "
041 ism). 042 lawlz), 013 043 runway-c rcctiiying willvl: lvo, Mullard t2 izllfifiilih 'JTBlllg " 3.
(l\|\\,) and 014, C44 (l,.\/\".);' rios IW4/350 01 Brim 3.2). Smoothing Q7 V45«(:-C°"l8 ~- "
inn-king by (:11 (sw I), (:12 (SW. ), by speaker tioltl L31 and condensers (6'; 3:33"? $51332; '~ 3:390;
015, 045 (M.\V,) and 046 (Il.\\.). R0- 028, C29. Hl'l~ Circuit RJK liltvring by Clo V iici'mlp lg .. 0-02
"VH0" hy grid coils L17 (S 20, L18 04. Main}; ILL filtering by 030. Film 3 w"""k" " "05
(mm), L19 (nut) and L20 (but). F1, in the form of a tw .pln plug, provides 5;; fifrfzfimg, 3:32,?
'Ihiul valve (V3, Mullard metallised \oltage fl( tment l (Ige and protects (1. can liner o-omos
VP4B) is n variable-mu RF. pcntudc the mains cuit from damage in case of (25 W~"|X"}"" 0 U-ulm
uporaling on radio as intermediate breakdown, Lin "lwm'ph'm " MM"
gm: (m '
or? m. M i
v v
Vii >11 11
in M
{an [m [m
_ _ :x cm
:5 sn
cal m
3/. Sit 52x
02 m
37 SH 512 I
KS ll CAI
CS! (3! CM) C2
, m
_ 319
n xu :23 .3:- w C _
M C33 EU a II? R2!
( 0 CI (no cu
5' 5] 1:5 in ace m m? Czl m m mt
,. cm
vs
il'((|ll(llliy amplifier with tuned»primary C' , d V f V l , '
luIiitil~5(~iviliilllly transfornwr cunplings hlrcu" gigram 0 the Decca 99 A'C' superh9[!,Wh'Ch
048, L25, L26, 049 and 050 L27, L28, as two W. ranges. Note the method of using V3 M
051. as an amplifier on Gram. Extra swrtclles, which we rm
Intermediate frequency 456K123 /5. do no: show, are fitted to short out (he cells not in use. N.
Diude second detector is part of separate (See Generalllotes.) . SIS

Page 2

January 8, 1938 THE WIRELESS & ELECTRICAL TRADER (Supplement) VII

Under-chassis
View All the
R.F. and oscilla-
tor coils are in
pairs on twelve
units, each unit
having a trimmer
at its and. C45
and 048 are the
M.W. and LW.

r trackers.

of the cabinet when .l)y lifting the back
r F r . ; ~ »- ,- - x v: A 'x, ' .
((tggIllfiI-zdi VIIR'IS )l"&(_"IQMII;IA\' £315; upwards, the (has < can be withdrawn
hv 7., ( m (ohms) to the e tent ol the speaker leads, which
«moo IIII éfvrimary " 17:27 i, ulli ient for nornnl purposes.
"'02 I] I ,I r . [0 free the rha. enthel unsnhlcr
0W, .1: .w.; mm y m. y,
u-I III iw v xi the speaker leads and urhm irplaring
, 13 .V .r s my on I .
~ by Is I 0.000! In S \rmlllmm'y or connect the lemls as fulh)\\s, numbering
000m III MW v-0 the tags Dom bottom tu {up WI, blue;
Cnupling m V4 A v. c dlnrl' , 0mm ' , l l .
4m couplinxtov _' 0m [.16 Is- 5 2, )lack; 4, rod, 3 and 5, no external
1 50.0 Hg 3 ; comm min
.. o-mn - l . - . -
1mm: Humble («memmnl II"! M. Rimming Spelakex. '10 runny , lo.
H T ll' 11 .fu \'- 7, l I 5}: (1 er runme L m nuts and loclx washers
} .1 smInn '1 (I :3; 3-. from the Sr. scrm - huldmg It to the
IBIIléunsurchl 155L332 .. I orlllW lnnmul M, Suh-halllc. nhm Tcpluzillp we that the
Aamlswffinnmw " I12: (millnmrl w. tIv-uIiwugvvviI .. M trzlmfnrlncr us on tlw loft
AcriallW. trimmer 25 N n tram. .. 71v
trimmer :12 i ~ -- 7: VALVE ANALYSIS
rv ttulung .. [2;]; lzml lJ 1mm. 7,
R.l mus memum »2 Q III . I . 7" Almrle l .~\n(nl<' sum-u 5mm.
W.1 krimlnrr sz ~ "4 SI" ' W" 15 ngv Voltage I (urmll Voltage Lnnull
.ALW. trimmer mu tlmu m-ulml. "fit 03 m mm W) (IIIM
MIN 1 W.triuunm Ifu .tnmlklrfivhlroll 1.500%» 7 . , I _I 7 _
. tuning I: Spl-nkcrnmut 4mm, VI vmn 200 7'» m, . I [I
SVVJ m'lmner tram. , Sr 'l M _ .
tsrwrz trimmer . wv' _ ( 'de 10 V2 ALI/1H1 2-5
()sc.clr\tnit M.W. trimmer "2 AL, gym 5 7x r
051: circuit LW trimmer "(Wk 'lII t n {5 v; Vld; m
Use. circuit Mwl tracker II , ~n 525 0 V4 2!) a ,
w tracker A WWSIW I ' ' V5 AC4l'cn :70
I lakorur rcul _:uniug W "W I . Vt» M. W, 12M
h I F. uaus. pri muing F"" MW" *3
. Scale lamp swmhc. ~ +1 wh mono, A (. _
49: U 5 sec: ""lg llllins swlk h gmgod [€24
(5°: "1 "1 m' V""". - Valve voltages and currents given in-
t511 2nd LP. trans.ser, (mung H # ,
the table above are those measured m
tElN-ntvlicv anrlahla :lm-sclr DISMANTLING THE SET our receiver when it was Operating on
A detachable hbuom ls fitted to the, malns of {20 \', usmg the 220 V tapping
Amm cabinet and upon removal (eight counter. on the mains transfonnm'. 'lhe 'recenar
\Hlues' sunk-head wood screws) gich a. gs to was tuned to the low melength on
(ohm) must of the components beneath the the medluln band and the yolume Control
*I 1 {SW IT V» chn as at In; 'lnmm, but there w my signal
, um I) l. o- . ~
1,: . HASH: __ 035 Removing chassis. 77 rt mum he "unit. .
1,3 AorialMHVlII muming ,. >5 necessary to rcmuve the Chaim from tho, \oltnges were meauretl on the 4nn\
:: Q:;;:{L;I2IIIIII=IIII"R_ . ~ 70? cabinet, remove the three small control s lleIal :1_ model 7 l versal .\\mnctor,
I}, Amalsw¢ nu"? il :: 0.1 knobs (recessed grub screws) and lhe CIHWHIN 'MI'll-I IcKHUVCr .
|.7 Aerhl M.W tuning I ,. 3-0 large tuning knob (pull ofi). Now remove H V2 slwuhl become unstable, :1: m
:1 lmlivsiwilxlxa :M ,. 117-0 the four Doll" (with washers and lmk our case, hen lts anode current is being
'9 pm y ' ' washors) holding the Chas. 5 lo the bottom Comimwd avrrleaf