Philips 634 a service manual 3
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Page 1
IO Service Engineer. Supplement to The Broadeaxter
Iammry, 1934
G.E.C. SUPERH ET FIVE
(Cont)
chassis. (Console, B01344). Suffix K
denotes Cetkin model.
Wiring Colour Code.i
Grid wiring, green; HT+, reed.
Anode wiring, orange; HTe, slate.
Cathode, pink; Earth, black.
Screening grids, blue,
Preliminary Tests.iFull eliminator
voltage of 530540 volts between two left-
hand tellminnls on speaker transformer. Volt-
age drop of 75 across field, left~hond (7) and
right-hnnll (+) terminals.
Removing Chassis.-Pull off the control
knobs and un-dn four screws from underneath
cabinet. Rubber washers may make them
seem stiff. Withdraw chassis, leaving speaker
leads connected for chassis tests.
Removing Speaker-{7&1 not, mzbolt
speaker from its own Imfllu, Unscrew the
baffle from the cabinet and undo the speaker
switch from its bracket.
Stand the set on the mains transformer end
for tests.
If trouble develops in any of the tuning or
intermediate coils the set should be returned
to the makers.
If one or more condensers in the block he-
come defective and suitable values of the
ta
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m_ B:
egg-gs wgB-~
fill u; _§ 5
Hoes ... ~3§s
as: $3
cscs CB
C8 CI7
cailfzz
BLOCK CONDENSER
small tubular type cannot be suspended in the
wiring the block should be removed.
All the wires are coded and it is immaterial
which led and white lead is taken to R2 and
R12. The condensers are identical.
As the full voltage drop across tile LS.
field exists between the case of 019 the can
is insulated from points at chassis otential.
Replacing the Chassis.71{ep ace and
screw up the speaker baffle. Replace chassis
and screw in the four bolts and press the
knobs on to the spindles
+
of?
7
TV
This diugrmn, in conjunction with the
condenser " key " panel, shows [he capacities
of the units in the condenser El 5 of the
Philips 634 A. _'
PHILIPS 634A
As a sensitivily control is ganged with the
tuning knob a] the Philips 634A. the scale
should be turned to maximum when taking
valve current and voltage measuremmls.
Circuit-The first H.172 valve V1 (S4171?)
is preceded by a. band-pass aerial circuit and
is coupled to the second 17.17, valve 172
(S4VB) by a tuned secondary HF. trans-
former. A similar transformer couples V2
to the diode section of the single diode
tetrade detector V3 (SIM), and true auto-
matic volume control is employed from the
plate of the diode to the grid circuit of the
first HF. valve. In addition, a cmnpensat»
ing sensitivity control R4 is made automatic
by gauging with the tuning mndensels.
The amplifying section of the S.D.T. valve
is resistance capacity ooupled to the grid of
the pentode output which is oompensated and
fitted with a manual tonermnhml threewuy
switch. The speaker is u permanent-magnet
movingrcoil.
Fullrwzue rectification is used, and smooth.
ing is by resistances R4, R16, R17 in the
negative H.T, lead in conjunction with
STRAIGHT
between R16, R17 provides bias for the
S.D.T. grid, which is decoupled.
Special Notes-This receiver appears
more complicated than it really is Philips
own slip-on resistances are used and are ob»
tainable from the makers (The soldering
iron should not he too hot.)
The sensitivity switch operates by connect-
ing R30 in parallel with R18 and part of R4
to lower the minimum bias on the H.F.
valves.
In some cases an extra condenser may be
VALVE READINGS
(Timing scale at mnz. Sensitivity switch out.)
25
screen
v2 sqvu} anode 5.5
sorevn
v3 541) anode .5
V4 PM24A anode no 15
aux.grld 203 4.5
. Tho resistance R 4 is ganged to the tun'ng,
and consequently alters the bias.
16 mfd. electrolytic condensers The tapping
CON DENSERS
Purpose.
1 Coupling to tetmde grid V s
2 Ruby-puma. ,.
3 Aerial input filter . .
7 Across valve filament ..
9
0
HT, feed to diode anode
Band pass coupling
21 Band pass coupling . .
22 Decoupling bias circuit V S
23 Anode bypass v3 ..
24 LF coupling v 3, v 4
26 Tone control V 4
27 Tone control V 4
28 Tone Corrector V 4 . . ,
29 Decoupling anodes V 1. V 2 . .
30 Part of AVG system ..
81 Dloue output filter . .
32 Decoupling bins circuit V 2
33 Decoupling SG, V 3 i .
34 Decoupling SG'S, v 1, v2
35 Decoupling anode V 3 , ,
36 HF decoupling uux. grid v 1
3'7 Decoupling grid, V 4 . .
as Decoupling aux. grid, V 4
89 Electrolytic smoothing . .
4o Electrolytic smoothing . . 16
41 short circuiting and across I.
and HF trans, . . . . 1.04
42 Short circuitlng and across LW
grid,v 2 ., .. .. .04
RECTIFIER " 5|!
c4 \ T
W 31 O V
6 . If 1
4/ I 0 2 3 -
132° m2 (:5 Ing 93 d 0
Em: o o g 1
=13 I
III
® Cl C6 9 TO E I
.6 .ml c, T 042 5%
l O 5E: °
C? 1 lo a. :
R28 C41 o.
r-: .911 O ___ I
TONE UCONTROL
Under chassis arrangement of resistances and condensers in ihe Philips 634.4 five-valve AC.
mains receiver. 0n the right is shown the layout of components on he and a] the sham}.
Page 2
January, I 934
Service Engineer. Supplement to The Broadcaster II
FIVE-VALVE A.C. MAINS RECEIVER
4; Y2 Y1
1- C5,, -
OF-1
_1_-_-_--.--_.-_-
GRAM.
C19
-,
W
B
L__.T._c'_7 _____________ _l
A unique feature of the Philips 634A receiver is the exclusive use of resistance: for smoothing.
c ""'l
4.
S
C25 22 253
S
C23
v+
R8
.1
R 'l
.4
C27
|.
i.
Altogether there are a large number of revision
employed, and this make: the chassis appear complicated. The construction, however, is planned for accessibility, with the mull that servicing
(Continued from previous page.)
found between the grid of the pentode and
earth in the position shown in the lay-out
diagram between 028 and 026.
The low A.Cr potential ends of 026 and
C27 of the tone filter may be connected to
earth direct instead of through the electro-
lytic condensers,
In some models a fuse is mounted on the
mains transformer; this is between H,T.+
(root. filament) and 039.
I hum is experienced, change round the
leads to the H.F. filter. .
Removing Chm .~Uhhtian:w First
RESISTANCES 3
Purpose. , 1
Part of AVG system
Grid Circuit 01' V 2
Decoupling and V 4 .
Auto sensitivity control
Dlode output pot.
- Pitt of AVG Circuit
HT iced to V 3 . .
,Grldleak,"4 .. .u
HF stopper grid. v 4 ..
Port of SJ}. feed
Part of 8 feed
Put of SC feed
mieedtoVSH H
m decoupler so of v 1
Bias pot. and smoothing
Bias pot, and smoothing
Decoupling grid, v 2
Decoupling grid, V 1
Decoupling grid, v 3 ,.
Grid leak tetrode grid, V 8
Grid leak, V 2 . u u .
Decoupling aux. grld, v 4
ET anode decoupler u
Part of diode output pot.
Part of AVG system
Part at AVC system ..
HTieedtoSG olV3 .r
Anode coupling, V 3 .
Seusit-lvity bias resist . . . .
Damplng Lw acctlon, m HF
transu , . . . u . , .
ewwwnnow
Poow~I¢-flpunuomm~leawaowmqanvlwuNI-t
wouwnnnwmnwnwwwwwa
uwmnnmnunnwnwunuuuwuw
is not diflicull.
tum var" ble condenser to min. and note the
exact reading A0 or 014
Remove valves. Disconnect earthing lead
to LS, Unsolder the leads to output trans-
former.
Remove screws from mains supply late at
top oi cabinet, and four chassis lolding
screws from underneath. Remove knobs from
front (grub screws).
In handling this chassis, take care not to
strain any of the containers not alter the
position of the wiring. Any alteration would
seriously impair performance.
Nolan-In the event of any trouble develop-
ing in the tuning coils, condense/rs, or the
small sealed trimmers, the set must be re-
turned to the makers.
Removing Speaker-.mDisconnect the
leads and remove nuts from the three clamps.
\Vhen a new cone and coil assembly is re-
quired, this can be obtained from the makers
M; a new clamping ring.
General Notes.-The wiring is not coded,
and when a component has to be replaced the
wiring should be labelled, To facilitate this
for the block condenser we have numbered
the terminals; the condensers give the con-
nections. _
The mains transformer mnnectlons are:-
Electrolytic condenser side, next baaeplate:
outers, set filaments; middle, C.T. Five
upper terminals from outside end HlT.-,
Beet. ('11., Fleet. Anode, Rent. fill, and Root.
Anode.
The mains connections are on the front
piano] and should be man-keel before dlsoon-
nectinge
Réassembling Chassis.rTurn conden-
ser back to minimum position and ruplaco
chassis in the cabinet.
Replace the loudspeaker and reconnect the
Wlles.
Check the calibration and replace four
holding screws and control knobs.
.c.i
How the coils. valves, HF.
filter and mains componenls
are arrangmi on the top of the
Philips 634A chassis.
MAINS
TRANSFORMER