Philips 225 b service manual

Page 1

2 Broadcaster Service Man's Manual October, 1938

PHILIPS MODEL 225B
PORTABLE

IROUIT.-iSclf-conlained frame Aerials escutcheon 5110 be lGmOVPLl, alldthe
constitute the grid coils and signal escutcheon plate taken off. when thls IS
picksuP circuits of V1, in frequency done the nut securing the pointer can be
changer. Provision is made to connect an taken Off and the pointer removed.
external aerial and earth system for use UHSOMEP the lead to the earthmg plate
in screened localities V1 is A.V.C. oon- near the gang condenser, the yellow lead
trolled, the potentials passing to the signal from mp grid {If V1 to the lap lag of aenal
grid my, the frame aerial windings. panel on side (inside) of cabinet, the yellow
An. iron-cored IF. transformer couples lead from the control shaft end of chassis
V1 to the grid of V2, an H.F. pentode to middle tag and the black lead from
operating as the LR amplifim V2 is control shaft end of clia§sis to bottom tag.
in turn coupled by a transformer with Then remove the two Chasss securing

t d d t L] d d 1 t' bolts from the brackets near the rear of _ _ -
digit offiycauaaroubfe dihede 530%; 3611:, the chassis by the speaker. The chassis $532,118,233: jsdlijfiltedwtiomméolgtlilllspl:
other diode of 373, fed by a coupling con- may then be Withdrawn sufficiently to model 2253 8% Ens. pomble.

denser 017 from the anode of the LF. obtain access to the underside components.
amplifier, provides the potential feeding Care _should be taken, When Withdrawmg
the A.V,C. network. chassis, to see that the pointer spindle and
The coupling arrangements to the grid Slégli.:llrenl}:tbs ft] t'd t' fV3'1d 1 Val e.~-. ismoune on_ ie

313113136] V312; 52311132,] om 1130c: :50": aerial panel on the Iside of the Cabinet. WINDINGS (DC-Ruixmflcfl)

. t d b . C29. C21 and R10 are enc used in the top grid . . v , .

Pore]? eis ryesistauce capacity transformer connector 0f V53 011$ 012: C15 and 016 1213; iOhms' mue"hemmeumd
fed to the pentode output valve 74. A are, of course, inside the cans housing the M,W. frame Low MAN Aerial panel.
pentode compensator condenser C25 am 55 I~F- transformers, C25 is connected L-W-fi'aln" 11 L Aerial panel.

, L1 .. .. M.W. Contactil l .
the primary oi the output transformer I amuse

gang.
eflects a fixed modification of tone. '
The receiver is operated «by an H.T. VALVE READINGS

L.W. (lac. gang and 08.

Ll+L2 22
L3 .. ii M.W. Contact 2 and
4
7

use. anode V1,

battery and a jellyracid accumulator. Na signal. Volume maximal». M.W. min. can. L4 .. L.W. Contact 2 d
Chassis Removal.-Remove back of New baumu. i K16(contal:nl)
cabinet. and take out the batteries Next Vi Type, F otmdei Volts, Ma. L5 .- .. ~ Aussie (grin V1
{{cmove the three grub-screw fixed control " All Mung. -* m .. .. 7 ¥ Toilngfia V2 and
nob! and the two hexagonal nuts scouring 1 FCZA _ . Anode _ s5 '5 mg.
the carrying handle, gen-zen .. 30 .9 L7 .i .. 7 - Angle (51/: and
The two tubular split nuts on the (in- , ECRROGe 30 1-4 8+ . '- ,
side) roof of the cabinet securing the 2 PZB " " 33:3: Z: :2 ; L8(part) " 5 _ Degfilg'éggfxeg
3 TDDZA . . Anode .4 LTi prim . a C24 and C7.
4 PM22A i . . . Anode , 4.3 LT. seci . - (724 and RlL
A E Screen . i .7 031. prim. . 600 - Across (:25.
c3; 3 _
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L7 L9 C20 23 RI?
| T2 c§9 3} RI!
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F 13.4

H -| C7 aces -- CIO a4 -- -- cm
H?! €25 Ems R7; gas
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Although a (our-valve super-he: arrangement, the circuit of the 2253 Is simple. The frame aerial windings form the grid
coils of V1, and the LF. mum-mars have Iron-cored coils tuned by fixed condensers.