Philips 747 service manual

Page 2

MULLARD

TUNERlN/Vfi'

VOLUME 0N~0FF «were

GE ours»: TONE CONTR OLloL/rs/Q In}

MAS7 [DIWAVECHAN
(umlmlell - C 9
ClO

cu

.@

MA/NS AER/AL xw

E

These two diagrams
identify the parts both
an to): and underneath
the chassis. HF wires
are bare. and care
should be taken not
to displace them.
Where they approach
each other. there
should be It least
ml inch clearance

W59

new

C3

REE

_ Fl: 0
C4@ Cmlcoggt'fifcgg '16
26' <~.v > LWLZSO 0

§ "5 L MC) swz ms

éz-a-r-a

M

@ VS L25
,/ L26

62469 @ @

MAINS

TRANS,
H VOLTAGE A01U$rM£~mec
Li t rr .
P. U. E.L.S.

3N 3/5; of GAE/NET

8w

TC R35
ul-

PW

Continued [mm page iii

by 627. R8 is in circuit on pickup only and
dc-serLsitises the V1 stage.

The oscillator section of V1 employs tuned grid
circuits comprising L14 (MW). 1.15 (LW), and
L19 (SW). R9 and C40 are the grid leak and
condenser, the latter being short circuited on MW
and LWA

From Vi an IF transformer, L20 L21, transfers
the signal to the grid of the variable~mu HF pentode
l\j/Z,C3"§his valve is cathode biased by R10 decoupled

y .

A second IF transformer. L22 L23. passes on
the signal to one diode of the double-diode output
pentodc V4. The diode load comprises R12, R16
and R13, the latter being the volume control.

From here. signals are fed to the control grid of
V3, a double-diode triode. via C33 (and C47 on
SW), R30 and R37. These last two resistors and
R23 together form the grid leak for V3. The
rectified 1F voltage across R13 and R16 is used to
operate the tuning indicator V5.

One diode of V3 is not used and is connected to
cathode. while the second diode is used for auto-
matic volume control and is fed from the anode of

iv

WINDINGS
L Ohms l L Ohms
l 30 . l6 . . , 4.5
2 275 l7 . , .. 9
3 very low 1 lx , . 40
4 my low 19 , very low
5 42. 20 135
t; 140 I 2l us
7 ~80 22 135
a 100 23 40
9 . .. 4.5 . 24 95
IO .. . 48 25 300
ll . ., 4.5 2t» .4
l2 .. .. 48 . 27 3.5
l] . . . very low 29 1
l4 .. .. l2 . 30 .. . l
ls .. H 40 l 32 .. ,. 175
V2 via C36. The AVC load is R28. There is no

delay voltage applied [0 the diode.

R33 connects the AVC diode of V3 to the second
diode 01 V4 and this diode is maintained at a slight
positive voltage from the potentiometer R1. R2
R35 and R36. Via a decoupling resistance R21.
The voltage on the diode of V4 is slightly above the

Continued on page vi

SAFETY IN QUALITY

The cost of solder [or a joint is so little
and a sound jomt means so much.
Whether you make 10.000 sets or
repalr l--be safefiuse the finest cored
solder m the world, Ersin Multicore-
the only 3-core solder. Our job is to
send you detailsAplease ask {or them.

MULTSCORE SOLDERS LTD-.mfiLLlER HOUSE
ALBEM/RLE STREET, LONDON.W1

NEW TELEPHONE NUMBER REGENT

FOR SA E BY
RETAILERS

More supplies are now
available at Multicore
6d. Cartons. obtainable
from factors only.
NATIONALLY Anvzx'flsnb.

1411 (P.B.X. 4

lines)

MARCH 1 946