The Gramophone Company 182, 172, 181, 171 Service Manual

P RIVATE A N D CONFID ENTIA L

“ His Master's Voice”

SERVICE MANUAL

FO R TRA DE U S E O NLY

for

F O U R-V ALVE

CONSOLE R E C EIV E RS

Broadcast Battery Operated Model 17 1
Broadcast Vi brator Operated Model I 8 I
Dual-Wave Battery Operated Model 172
Dual-Wave Vi brat or Operated Model I 82

T ECHNICAL SPECI FICATION

B ATTERIE S

Model “ A ” Supply “ B” Supply

171 & 1 72 2-volt I 10 amp. hr. I x45-volt & I x60-volc

Accum ulator. Superdyne Battery.

181 & 182 2-volt 190 amp. hr. Vibrator.

Accum ulator.

The accumulator, where supplied with the re 

ceiver, is already fu lly charged.

This battery should be recharged at least every

tw o months, or, alternatively, whenever the specific

gravity as measured w ith a hydrometer falls below

1.140, o r the voltage, w ith the receiver in operation,

falls below 1.8 volts.

C O N S U M P TI O N

Model “ A ” Supply "B ” Supply
171 and 172 0.37 amp. 11.4 ma.
181 and 182 2.2 amp.

I N T E R M ED IA T E FR E Q UE N C Y

457.5 kc.

S PEECH O U T P U T

135 m illiwatts into voice coil.

W AV E -L E N G T H R A N G E

Models 171, 181: 187-545 metres (1600-550 kc.).

„ 172, 182: 187-545 metres (1600-550 kc.).

13.9-47 metres (21.57-6.38 me.).

D IM EN SI O NS

Height,

W E IG H T

Model

,, , ,

Model 172

, , , ,

,,

Model

,, ,,

Model

,,

35ii

n.; w idth, 30{in. ; depth,

171

,,

" A ’

Battery .. I7 i ,, 20 ,,

••B'

59 lbs.
26 J ,.

61 „

“ A ’

,, “ B’

181

’ Battery ..

“ A'

.*

Battery ..

I7i „ 20 „

26Ϊ „

68 ,, 80 „
25 „

182 68 ,, 80 „

“ A ’ Battery .. 25 „ 28 „

Net

14in.

Gross

71 lbs.
28 „

73 „
28 „

28 „

V AL VES

IC7G C onverter.
ID5GP I.F.

IF7G Dem odulator, A.V.C. and 1st A . F .
KL4G Power.

LO UDSPEA KER

The speaker used is of t he pe rma ne nt magne t
dynamic type. It is a 8-inch mod el with a vo ic e coil
impedance at 400 cycles of 2.4 ohms.

CI R CU IT DESCRI P T I O N

These models em ploy a 4-valve superheterodyne
chassis comprising a Pentagrid converter followed by
an I.F. amplifier. Demodulation is effected and
A.V.C. voltage is obtained in the diode circuits of the

following v alve, wh i c h is a duo- di ode- pent ode; th e

p entode s ec t ion of this valve f unc t ions as an au d io

am plifie r a n d is r esist a n c e - c a p a c i t y coup l ed to the
ou tput val ve , which is o f th e p en tode typ e .

Couplin g to the aerial on the broad c a s t band is
eff ect ed through an iro n-cored trans f or m er having
th e n ormal t uned s ec o n d a ry and added capaci ty
b et ween t he high po t enti al ends of prima ry and
se condary .

The I.F. tra nsf or m ers are pe r meabil i ty tun ed and

empl oy L i tz- w ound coils with sli d in g ir o n cores.

Full A . V .C. v oltage is applie d to th e conver te r

and I.F. va l ve w hi ls t par ti a l A .V. C . is take n to th e
au dio v al ve; no A .V.C. v olta g e is appli e d to th e
S . W . con verter gr i d.

Pa dding is ef f ected by a djus t men t of the oscil l a t or

se co ndary inductan ce by means of an adj u s ta b l e i ro n
co r e, in co njunctio n with a f ixed padding con
de nser. N o pad din g adju stment is req uired on the
S .W. b a nd.

Al l R.F. tri m m ers are o f the ai r die l ec t ric type ,

using a ro bust pl ung er typ e const ructi on , w h i ch is

e nti rely im mun e to change of cap acit y by a tm ospheri c
inf luen c e s.

W he n t he chassis is op erated with a vi bra to r
un i t , the bias on the po wer val v e gr i d is obtain e d
from the vol ta ge drop across the sm oot hin g c h oke in
th e H .T. neg at ive leaa.

W hen oper ate d wi t h batte ry H.T. , this bias is

der i ve d fr om a vo l t age aro p across a re s i s t or in the
H . T. n eg at i ve le a d.

Th i s ch a nge o f c i r c uit co n nec t i o ns is au t o

matica l l y acco mplishe d bv s l u g ging t h e approp riate

cable into the proper ba t t ery sock et on the chassis.

By t his me a n s it is possible t o co nv er t M o dels 171
and 172 int o Mod els 181 and i82 re spectiv ely by merely
plugg i n g in a vi brat or un i t c a ble in place of the
b at ter y cabl e .

Pick- up conn ec t ion is p r ov i ded for by two pin

jacks. I nserti on of pick-u p in cir cuit a uto ma t i ca l l y
shorts out t he dio de loaa, thus preve nti ng inter
fe rence from br oad cas t signals.

C A U T IO N

It is no t a d v i s a ble to a lter the leng t h of a n y of

th e bat tery conne cti on caoles, because the ir re s i st
ance f or ms par t of the total seri es resis ta n c e intro
duc e d t o obt ai n c or rect fi l am en t voltages .

W A V E -B A ND SW I T C H IN G

(Mo dels 172 and 182)

This is c ar ried out by means of a two-pos i tion
swit ch. The os cilla to r pri ma ry coils are co n n ect e d
in seri es, as are th e aerial prim aries, and are not
swi tc hed ; however , a lit tle f eed-b ack is app l i e d
across th e padd i ng conden ser on the S. W. band , and
this is swi tched in and out by c onta c t s on th e wa ve-
chan g e s wi t ch.

In the first p o siti o n of the switc h ( an t i - cloc kw ise)
th e receive r is ad ju s t e d for short -w av e rec ep t i on,
and in t he seco nd po s it io n for broa dcas t re ce pti on .

T O N E M O N IT O R (Combine d wit h Battery

Swit ch)

The tone is c ont ro l le d by a f ou r-po sit i on switch,
the fi rst po s i t ion o n which s witc hes the rec eiver off ;
the sec ond p o sition swi t c hes th e re ce i ver on and
gives no rmal re pr oduc tion, whi l e the thir d a n d

fourth p o sitions i nt ro duc e an inc re a s in g deg re e of

hig h- frequ enc y cu t by means o f a conde nser resist or

com b in ation shun t e d across the speake r tr ansforme r
pr imary.

DI A L LA M P (2.5- v o lt , 0.3-a m p .)

The dial ligh t i ng is con trol l ed by a p ush-butt on
mounted on th e s id e o f the ca binet, whi c h s hould
be pr e ssed during the pro ces s of t uning - i n a s t ation.

W hen r elease d, th i s but ton w i ll ext i ngu i sh the dial

light ing , th u s saving unne c es s ar y dr a i n on the
battery .

PRELIMINARY TESTS

VIBRAT OR C IR C UIT DES C RI P TIO N (Mod els

181 and 182)

The c ircuit o f the vibrator unit is in di cated on
page 6. Th i s un i t i nc lu d es the v ibrator c artridge,
whic h is e n c l o s ed in a sepa r ate m etal container

arranged so that i t can be p lug g e d int o o r re m o ved
from a socket lo cat e d in the vibrator unit in a man ner
simi l ar to a valve. T he vi brator so ck et is a rran ge d
with a sp o n ge rubber m ount i ng , to ens ur e a
m i nimum o f me c h a nica l noise b e i n g transmit ted t o

the cabin e t .

The re m a i nder of the uni t consists o f the ne c e s 

sary tra nsformer s and f i lt ers .

Im por tant Note.— It is essent i a l t h at th e

resis ta n c e o f t he 5-a mp . fuse in t he vi b r a to r pos i t ive
L.T . ci rc ui t sho u l d no t excee d 0.01 ohm, o ther w ise
th e perf orm anc e and batt ery life w ill s uff e r. Use
on l y Aust ra lu x 5 - am p. fuse, typ e IAG .

1. Check ov er bat t ery conne ctio ns in ac cor d ance

with the dia g r a m on page 6.

2. Check ov er batt ery vo l t a g e s as sp ec ifie d in para
g r aph heade d "Ba tteri e s.”

3. Rem ov e fuse from A + vibrat or lead and che ck

fo r cont inu ity in the fuse (M od els 181 and 1 82).

4. S w it ch th e re ce i ve r on by means of th e com 

bi ned Ba t ter y and To ne Moni tor S wit ch , a nd.
havi ng remo v ed th e e arth w ir e and t urne d the
Volum e Cont rol t o t he ma ximum p o siti on, t ouc h
th e finge r to t he gr i d of the IF 7G valv e (1st AF).
A l ou d h um sho u ld be heard; thi s de no t es that
the au dio frequenc y side of the re ce i ve r is fun c
tioni ng and the fa ult prob abl y lies in the valv e s
or as so c ia t e ci rcui t s ahead of t his posi t i o n. Sh oul d
no hu m be hea rd, the fau l t wi ll have dev elope d
b etween the fir st au dio and o utput stage.

DI SMANTLING

REM O V A L OF C HA SS I S

1. Remove knobs.

2. D i sco nn ect loud speaker and ba ttery plug.

3. Remove the t w o leads from the dial lamp s wi tch

on the side of the cab i n et.

4. R emove t wo fix i n g bol ts from un derside of the

shelf; the chassis is now free .

5. Check all valves f or fil ament continuity and free
dom from in t er na l sh ort cir c u it s .

6. T o de ter m ine if the faul t lies in the l oud spe aker,
connect a high- i mp edanc e A .C. voltm e t e r or
o ut put met er , wi th a range of a pproximately
2 volts , across th e voice coil te rmin als o n t he
sp e ake r . W ith t he re ce i ve r s witch ed on and
adjuste d f or the bro a d c a s t band, turn the Volume
C ontr ol full y on and ro ta t e the Tuni ng C ontr ol.
If no defle ction is giv e n by th e m eter, t he faul t
lies eit her in t he r ec eiver chassis or th e out put
tr ans fo rme r. If a d e f l ecti on is obt ained, but no
audib le so u n d , the lou dspeak e r is at f aul t.

7. If th e f au l t is still undi s c ove red , remo ve t he
chassis from t he cabinet and compa re volta ges
w ith t he v oltage table giv en on page 7.

REMOVAL OF LO UDSPEAKER

1. Remove spe aker plug from rec eiver chassis.

2. R e mo v e f our sc re w s h o l d ing sp eake r chassis and

re move s pea k er.