Philips 472 a service manual

Page 1

llTllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll lllllllIllllllllllllillllllill :lll ill I lll Il

"TRADER SERVICE SHEET

680

,l.illllillllllllllllllllllllllllllllllllllllllIIllllllllllllllllllll lllIllllllllIIllIIllllilllllllilllilllll-I llllllllll u ll,

The Philips 472A,

UUR \flillilille'fiullCLl sigi :il IrIu
quency r-ircuits are employed in the
Philips 472A. .3 5'\ELlVe Iplus rnctv
Ilci-I TRF Suprrinrlinwnicc " ieieiwi {It
signer] tor operation from AI' inaim (f

100250 Y, 407100 r, 5,

An almost iiloiiticail clmsais la t|l|ltl1l3vl
in the Philips 577A receiver. the (ii-Fir
mica lieiiig explained under 577* ml:
Iii'utinns overleaf. This Maw-ii. N/Im
liowevei, was actually prepared from I
472A TeCehLi.

Relilas-r {1am and original [mm < 472 I,
l934. 1,15 l5x.,- 577,]. 1955, 1]? 73m

Supplement to The "Vivalws (3"
Electrical Trader, .7iily is, 1944

PHILIPS 472A -

SUPERINDUCTANCE AC RECEIVER

CIRCUIT DESCRIPTION

Aerial input is via seiieb condensei 01
iiiid chokes L1 (M\V) and L2 (LW) to top
pings on primaiy winnings uI' iapamn
t-uuliieii quui.pus.~ filter. Prunal'y coils
L3, L4 are tuned by 033; secondaries L5,
Ls hy cas; coupling liy tommon iinpw
dance ol GE (KIWI, plus, 04 (TAYI. iii
primary and secondiii circuits

R1, 61 Klllllll the ac til circuit on both
bands. Mains aeiial coupling via (:3, 81
directly to aerial smkm A is effective Sn
qug in uu min is connected, but when
ihc- uel'iztl plug is inscrLud. S1 automatit
atlly opensi

Fiisi \ali'e (V1, Mullam metallised
va (spun) is a talltllile»mu RF pen
tode operating as signal frequency ampli
Iier with tuned-sewndary RF transformer
I'Unliling by L1, Ls, L9 um] (:39 to u
mound Valve 01' the some type (v2, Mul-
|ard metallised VPIIA [5-pinl), which in
turn is tuned-secondary RF transformer
imipled Ir) L10, L11, L12 and CH to ii
spliaiztte double iliorie detector valve (V3,
Mull-rd metallised 204A or 2D4), om:
Ilimli- nl uliiuh is not used.

St: and GB puientiiils for V1 and V1
til obtained from an HT potential divider
H H5, H6 Riki R1, the lust of which is
\iliiitliit and is ili'i\eii by the timing con
Irol drive to level the gain over the bond
in use In) suitably adjusting the GB of
V1 and V1, the GB increasing as the
wavelenglh is reduced. Minimum (1B
potentials ure- imposed hy the drop across
R9 (for V1) and R12 (for V2). 0n MW,

55 lanes, sliiirtri'iicniting R8 uuii reducr
iiig the standing lili value-

.-\uili0 frequent-i i-uniponent in i'eI-tiIietl
uutpnt Irom V3 is developed across R15
antl illf manual volinne rantrul R16, which
also operates as lnml , or, dllti passed
Iia, Al" coupling minimum 018 to CG M
a thin] RF pt-nlnile (VA, Mullurd metallised
spa) quui. UpuinLvs as AF amplifier.

l)(l pun-uni] uppeitl'lug 3 vi- R15 is
tripped on and Teri hutk riu tlutoupliug
circuit mu, cw to v1, ulviuu :iutuniitlic
volume ruiitiul Provision for the coir
uuuiiuu or a ui-uuiuuiuiue piukup by
sockets Bonnet-toil via 53 ttCIUSS R16, 83
closing mi 59 upuuiuu when the i'untrol
is turned to the grain position.

Resistance capacity ioupliiigr by R21,
624 and R22 between V4 and puntode
output valve (V5, Mullam PenOVA).
Fixell tone correction by 021 and Variable
tone ontrol by R25, 026 in unodr LITCIIII.
Provision i: also made in the anode cirr
cuit for connecting a high impedance
external spvakor, while SWItch $10 in the

specch coil circuit permits thr internal

speaker to be united.

RF filtering is progressively applied
through several stages: 019 in V4 (IG
circuit, 021 iii VII anode circuit, and R23,
025, R in V5 [70} circuitr followed by
the grid/cathode capacitv of V5.

HT riirrent is Suppl ii by I'iillrwiive
rectifying valve (VG, Phllip: 1821 Ul' Mul-
lard DWQ). Smoothing by llUthOIQd
(lioke L11, in HT negative lead, and eletu
trolytic Condensers 618, 629. Mains input
filter chokes L15, L16 suppress RF inter-
ference

Circuit diagram of the Philips 4~2A TRF Supcrinductance" AC receiver. Several features are concerned only with maintaining
I constant sensitivity and selectivity throughout the two wavebands employed. These include the two aerial series coupling chokes L1,
L2, with Cl, C2, 5 variable resist R7, which is ganged with the tuning control drive, and the switch 85, which closes on MW to

1 short-circuit R6. In [hrs connection also, VI and V2 cathodes are returned a common point (in the HT potential divider R4-R7. '

.,