Philips 714 b service manual

Page 1

50 Broadcaster Service Mans Manual

PHILIPS MODEL 714B
BATTERY FIVE

LEOUIT.-An inductively and capaci-
tively coupled bandpass filter
couples the aerial to V1. an H.Fi

pentode, on medium and long waves on
short waves a single inductively coupled
tuned circuit is used. An image fre
quency filter consisting of CKl and T5
is included in the aerial circuit.

A separate triode oscillator is employed
with an orthodox coil circuit, injection
being to the suppressor grid of V1.

The output oi V1 is coupled via an 11F.
transformer tuned to 128 kc. to V5, an
HiF. pentode, which is in turn coupled
through a second 1.1. transformer to V4,
:1. double diode mode.

The primary oi the second I.F. trans-
former is centre tapped and is coupled
through a small condenser, 051, to one
diode of V4, which is used to supply
A.V.C. bias to the grids of the preceding
valves in the orthodox manner.

The other diode is used for demodula-
tion, the LR output being fed through
a resistance and capacity stage, which
incorporates the volume control, to the
grid of the triode section.

The grid circuit of V4 also includes :1
muting condenser, 033, which is brought
into circuit by depression of the volume
control kndb.

Coupling to V5 tnhe Q.P.P. out ut penv
lode is through a capacity couple QiPJ.
transformer. Grid bias for this and the
preceding valve V4 is obtained from the
battery.

The amplified output of V5 is fed

ALE _ _. __
51,

$2

through a matching transformer to the
moving-coil speaker.

H.T. and grid bias are obtained item a
combined Ever-Ready Portable 59"
and LT. from a. 2-volt 20»amp. hour
Oldham accumulator, type ZLG5.

Special Notes-Sockets are provided on
the back of the chassis for connecting an
external speaker and a pickup The
external speaker connections are taken
from the primary of the output trans-
former and an extra speaker should
therefore have its own matching trans-
former.

The pickup connections are via the
volume control to the grid of V4; a
switching position is provided so that the
pick-up may be permanently wired in
circuit.

When the receiver is operating on short
waves the oscillator frequency is 128 kc.

VALVE READINGS

Nn fiiIVnal. Volume maximum New batteries
TY]
All 111111th

leotlod

1 VP2 mend) Anode . 145 111
Screen .. 115 .25
2 PhéifiLmetl Anode .. 70 1,75
3 no mot) Anode ,. 135 1.55
Screen ., 130 .3
4 TDgZAmet. Anode ,. 100 .s
5 opium) 4, Anode)1 v 145 1.1
Screen) L 118 .09
Anode) ( 145 11

Some; 1118 309

April, 1937

The Philips 7143, a superhet all-wave
battery five with Q.P.P.P_output.
lower than the frequency to which the

HF. circuits are tuned, the object being
to prevent oscillator drift.

Special arrangements are made for
correct matching of the two sections of
the output, valve, by means of letters
etched on the glass bulb and correspond
ing to H.T. voltages.

The two sections of the valve are
identified by means of the letters A and B
stamped on the side of the base, above
which will he found the battery voltage
lettersJ these being as follow: T, 133.5
volts; 8, 128 volts; B, 118.5 Volts; Q,
111 volts; P, 105.5 volts.

Removing Ghassis.-Remove the four
knobs from the front of the cabinet (grub
screws) and unsolder the earth lead
between the chassis and metallised paper
base of the cabinet.

Undo the adjusting screw and release
the Bowden cable from the waverchange
indicator. Slacken the screw securing the
pointer to the wire and the two slotted
nuts, one on each side of the scale. Then
remove four screws which will be found

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Vllve arrangement of the 7141; is Hr. peniode, triorle oscillator, LF. pentotle, double-diode-triode and Q.P.P. output. The H.172
liner is band-pass on medium and long and a single circuit on short waves.

Page 2

April, 1937 Broadcaster Service Mans Manual SI

in two brackets on either side of the scale, primary and the primary while trimming !

just above the adjustin screws for the the secondar . h. .
tuning drive Bowden cub es. LP. Glrcu ts.-Switch the receiver to P lllps 714B
Finally, unsolder the s enker connecting long waves, tune the gang condenser to
leads and remove four galls from under maximum capacity and short circuit the on Test
neath the cabinet and the chassis may be oscillator gang.
completely removed. Connect a. modulated oscillator timed to ODEL 714B.-Stsndurd model
it should be noted that this cabinet, is 128 kc. to the grid of V3, via a .032 mid, for battery operation," using
fitted with a removable fibre base plate condenser, and an output meter across the EV Ready Portable 59 H-T-
which is held in place by four small bolts. external speaker terminals. gage? and (ilihauia type ZLG3
Most of the work necessary may be done Use a. .01 mid. shunt condenser and Diisclzitirgigiv Virlguebvafigs 115
without removing the chassis. trim T1 and T2 for maximum output. oscillator haltery snperhbt tgble
. . . Transfer the oscillator lead to the grid of v1, model wfih walnubfinished cabi-
Circuit Ahgnment shunt the secondary of the first 1M. with a
10,000 ohm resistance and trim T3. Remove _ Strai 1H. f 11_
the shunt _ .- gi me u
Notes Shunt the primary with a 10.000 ohm resist vision sen e'Wltll name and wave-
All the trimming wudenm. adjusting ance and a. .1 mid. condenser in series and trim length calibration. Scale not

T4 {or maximum output. Remove the shunt illuminated. Variable selectivit

screws are 39311911 With Wax, Whldl must and repeat the adjustment of T3 Then control ganged with lone. Pusi
he softened With a warm soldering iron. readjust Tl. action muting switch on tuning
Great care should be taken when adjust. LF. Elliot-Transfer the oscillator. still tuned knob. Tone control concentric
mg the trimmem, otherwise the wires 2115:.195'f3,f,fi,3%3fii1fi$mmm d with band width control. Volume
soldered to the heads oi the adjusting Medlum w,,,¢,___pram .015 deg. mph, concentric with wave selection.
screws may he broken. in position and adjust the gang condenser Internal aerial selective by EDS-

In the are; 'below mention is made of against it. If the template is not on hand. then LoiniNG.-L.T., .95 amp.; .T.,
a, 15 de tem late and an an iliar tune the_recelver ~19 206 metres (1,442 km), 7,5 ma.

. 8- P . 3 . Y meet a signal oi this wavelength to the aerial . . . . .

amplifier. The template is for adlustmg and earth terminals via. a dummy rerun and Sens-My and Select-My
the gang condenser to a. required capacity zidiusl. T6. T7 and TE lor maximum output. SHORT WAVES 05:5'52 metres).-
and may be obtained (from Phili 5 service Long William-Tune the receiver to 760 metres Gain and selectiv1ty very good.

- - (395 kc.) or edit the condenser against the Egg handlin no drift. ain well
department. The smpllfier 1 only be template. Inject a signal of 760 metres and mnlhtalned o§ér wavebuni.
needed if the receiver is badly out of adjust T9 for maximum ouhplllr. MEDIUM Wives (1907585 metres).

an and can be the rumo hone side of Image Filteralnject a strong signal of 300 - - - . ~ .
in greliahle radio setg [3 metres (1.000 k0,), tune the receiver carefully to fSenSitwity and selectivity MY?!)
1% . w . the second channel whistle on ivpproximawli' lush Order- In maximum 1008mm
0" LE lmmmg various shunt ' the band Width gives excellent

resistances and. condensers are required fidelity whilst in minimum selec-
tlie procedure being to shunt the secondar}; CONDENSERS tivity Will $9!th adjacent
(7

of one transformer While trimming the . l Purpose. Dim. 013915-, Overlap only presemon
. 7v local stations. Background quiet.
15 Top blind pass coupling .. .00001 Whistles very slight.
RESISTANCES if; 3:33 resuming": -~ l- fig; LONG WAVES (725-2,ooffio).-very
-'-~'-"- W m? 3 '~ high gain selectivitv su cien to
is s.w. d 'l h t.. .. .00002 . . l .
PM]: 19 V1 fillfiiflgxtiflgun .. .. .0001 give Deutschlandsender with sub

stdntiully no interference. Gain
and selectivity Well maintained 1
over wnvebund.

v1 grid .. ..
v1 suppressor grid leak

R

1 20 V1 screen decoupling
2

2 V2 anode decoupling

1

ti

7

B

21 v1 suppressor grill couplln"
22 Osr gang series

V2 anode deconplin 23 L. 090. padding .
v2 grid leak ., 3,. 24 pudding .. Acoustic Output . r .
v2 grid stabiliser . .. 40 25 . W.osc padding Very good for single lngh slope 1
V1 and V3A.V.C. decoupling .5 meg. 26 grid .. pentode, illustrating the value of .
Volume control . . . . .5 meg. 27 A. C. decoupling tone-com ensuting circuits. Sulfi-
0 V4 grid network part .. .2 meg. 28 Ill. filter .. cient v0 me for medium mom i

10 v4 grid network pert .. 1 mg, 20 LF. coupling . . . lliout 0v er} 0 a din

11 v4 grid network part . . .2 meg. 30 L.F. filter .. .. . . .0001 W 3- l

12 A.V.C. diode loud (purl) .. 1 meg. 31 Arvrc. diode coupling .. .0001 _ . ,

13 A.V.C. diode load (part) . . .32 meg. 32 LR coupling . . . . .05 40} metres and trim T10 101' mzmmnm output.

14 V4 unode loud ,. .. 25,000 33 L.F. transformer shunt .001 short Wavee.-Thcre lore no short waive

15 Grid blue network (part) 1 men. 34 V4 anode decoupling adjustments on_this receiver, the circuits being

16 Grid bias network (part) 20,000 35 Tone control .. permanently adlusled by the makers.

i; grlg iii netwmé 21mg; . . 5,000 3? lift. shunt 0009:): ---~

ri as he wor r . . 10,000 3 mega suppressor . .d . .

19 V5 grid stabiliser pi. .. .2 meg. so Muting ,. .. ., .01 . Anfixaci FePIMEWm 9°delsleilio'fcz6

20 V4 nunde decoupling .. 3,000 39 Pentode compensating .. .001 in this Phillips receiver is awm a e ram

3% 33m: antic] ,. H .. .. 50,000 40 Pentode compensating .. .gggoom A. H. Hum, Ltd, of Garratt Lune,

_ an e ecoup rig .. 4,000 41 v3 screen decoupling ,. . . -

23 v3 screen decoupling ,. 20,000 42 v3 anode decoupling .. .005 wandw°h- Lona) SW 1 number

5,472, it is priced at 25. 9d.

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HFGANG
OSCGANG FRd-w (i c2: 05%
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1.1-1? %% C25
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Chassis layout of the Philips 7143. The tinted diagram (left) is the top; the right-hand diagram is the underslde.