Philips 206 a service manual

Page 1

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TRADER" SERVICE SHEET

478

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valve rectifier) 3rband AC super-

het, suitable for use on 10mm»;
50-100 C/S mains. The SW range is
16.7-51m. The receiver is fitted into a
compact moulded cabinet, the inside of
the top of which is covered with metal
foil, which is used as a plate serial for
the reception of the more powerful
stations if desired

Itcleuxr: date: May, 1940.

CIRCUIT DESCRIPTION
Aerial input, via coupling coils L1
(SW), plus L2 (MW), plus L3 (LW)
to sin le tuned circuits L4 (SW), plus
LS (MW), tuned by (:31 or L6 (LW)

THE Philips 206A is a, 3valvo (plus

tuned b 631. Condensers Cl and C2
shunt and LW coupling coils rcr
spectivoly. while unwanted coils are

......-..
, run my»

3cm UMP

Supplement to The Wireless &
Electrical Trader, August 3. I940

PHILIPS 206A

3-BAND AC SUPERH ET

shortcircuiicd to chassiis both in coup
ling and tuning circuits.

A metallic foil sluck inside the roof of
the cabinet is permanently connected
viii a contact strip to the aerial socket
of the receiver to pennit the receiver to
operate Without an exlernul aerial if
desired.

First vslvc (V1, Mullard ECH3) is a
triode-hepiode operating as frequency
changer with internal coupling. 'lriode
oscillator anode coils L11 (SW), plus
L12 (MW). plus L13 (LW) are tuned
by CS5; parallel trimming by 013 (SW),
833 (MW) and 034 (LW); series tmok-
ing by 012 (MW) and 032 (LW).
Reaction coupling by L8 (SW), plus
L9_(MW), plus L10 (LW) via dsmping
resistance R7.

IF suppression by tuned filtcr rciector
circuit L7, (:5 in V1 heptode control grid
circuit.

Second valve (V2, Mullard EFS) is a.
variable-mu RF pentode operating as
intermediate frequency amplifier with
tuned-primary. tuned-secondary iron~
dust cored transformer couplings C8.
LIA, L15, CS and 018, L16, L17, 019.
Tuning adjustments are made by suit-
ably positioning the threaded cores in
the coils.

Intnrmadiats frequency 470 KC/S.

Diode second detector is part of
double diode output pentode valve (V3,
Millard EBLl). Audio frequency com-

ponent in rectified output is developed
across manual Volume control R15 and
its limiting resistance, R14, which
operate us load resistance, and passed
vis the AF coupling condenser 025, CG
resistance R16 and grid stop I R13 to
CG of pentode section, IF tering by
021 and 026.

DC potential developed across RM
and R15 appears also across R12, R13,
which are connected in parallel with
them to form a. potential divider, from
which the AVG line for V2 is tapped
off and fed back via. decoupling Circuit
to the valve grid circuit. giving uni
delayed automatic volume control.

Second diode of V3, fed from tapping
on L16, Via small coupling condenser
624, provides a. second DC potential
which is developed across load resistance
R21 and fed back through decoupling
circuit to CG of frequency changer, v-
ing delayed automatic volume contra in
this case. The delay voltage, together
with GB for pentode section, is obtained
from drop along resistsnces R19 and
R20, which form a, potential divider in
cathode lead to chassis

Fixed tone correction in V3 pentode
anode circuit by I321.

Part of the output voltage. ,as. it
appears across the secondary_w1nding
0 the on ut transformer T1, is topped
off and fe brick to the cathode circuit
of V3, where it is interposed between

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Circuit diagram of the Philips 206A 3-band AC superhet.

Note the plate aerial and the IF rciecmr in the

heptode control grid circuit of VI. No smoothing choke is fitted, smoothing being carried out by (:23, R" and

C29.

Slight modifications in Tl , and in the heater secondary of T2 may be present (Sec Chassis Divergencies ).

Page 2

Under-chassisview.
The Sl-Sll unitis
built on to a paxolin
plate which sup-
ports the five coil
units A diagram,
looking at it in the
direction of the
arrow, is in column
1 overleaf. :32
and C34 are small
wire-wound adjust-
able condensers.
R IT is a wirerwound
resistor.

the oathnde and the biasing circuit to
introduce negative feed-back.

H'l current is supplied by fullrwnvc
rectifying valve (V4. Mullard All).
Smoothing is effected by elegztrolylic
condensers 023 and 029 in con1unction
with the HT feed resistance R17.

DISMANTLING THE SET
Removing Chassis.ifiemove the three
control knobs (recessed grub screws)
from the front of the cabinet;
remove the screw holding the plate
aerial lead. with its contact strip and
small subrbafile Clamping bracket _to
the moulded projection on the inside
front of the cabinet;
remove the clip [roundr
hen/d wood - screw)
holding the mains
lead tn thn floor {if
the unbinel.
remove the two set-
sc rc w s (with
washers) holding the
scalp. assembly to the
front of the cabinet;
uiisolder the three leads
from the, speaker Con-
nmling strip:
rolilove the four bolts
(with washers) hold-
ing the 1lJaGiilH to the
bottom of this ziliiilel.
lVlim ruillucing. lin-
baseboard should be
so placed thnri the
totally screened Mdc

Lil

feces dowmmrds; the
he (1r{ end zit Whicli tho

screen overlaps liii (u

the upper side should
be on the right- when
5. \leud (min the rvlu'
,/ of the (albinlt
Connect the plain

A ( WM yellow speaker lend
\ to ',h( lblt-hnnd mg
\ «m lhw speaker mn-
su nmlmp amp, 3"
-) VlCWCfl from Iliw

Supplemenl [(1 The WIIIILM $2-
Elc-rlriialllrgtflgdugur: 3. 1940

war of the rig-river. and [he wmnd
yellow lead (Vl'ilh ll QN'tu splash near
the end) lo the middle tag.

The blank lonrlhing) lend gar-s lo the
right-hand tag, which is clamped
under the top fixing nui.

Removing awaken-Remove thr- three
nuts (with washers and lockrnuts)
holding the speaker to the sub-brittle.

When replacing. a lock-washer should
he placed under the first nut on the
top bolt, and the speaker connecting
strip, with the earthing tug directly
beneath it. should be fitted hetworn
the two nuts.

COMPONENTS AND VALUES

(1m: lmNsnns 1"?
(id)
l
l
Cl Aerial MW shunt l 0 000039
(:2 Aerial LW shunt . . li-mmg
()3 Aerial circuit LW trim -0000039
l (:4 Vi iii-made CG conden n arms
(75 IF rejectoi tuning condenser o-txmu
l (0 Vi lIl-IthdP (Xi demnpling 0-047
3 07 V1 56 decoupling .. . u-oii
C8 i let [F transformer J n omloa
l (I!) I tuning condensers r 0 000097
(10 Vi mm CG condr-n. r ' 0 00m
('11 Vi cathode by-p u an
012 One. circuit MW mi in workman
. C13 05c. mom: 5 trnnrnr-r o-uvmzz
(14 i Vi one, amide mnpling mum
(l5 1 V2 C(l llcccirnlmz .. .. 0047
cm GB cur-nit lJy-ilaas ., 0-1
on v2 nu uncoupling ., .. 0-1147
C18 r 2nd ll" lrraiislbniivl r o-mmm
- cw f tuning condcnscru r o-lmios
; (20 V-2nnurmleliy-nan , 0-047
r (:21 IF bypass ., 1 women;
, 022 lurt or nigntivc {is (His: ii .
l coupling . . .. 00:7
023* HT smoothing crinrlenn r . iii-ii
U24 . Coupling to V3 AW: diode 00000031:
C25 AF coupling tn \':i peiitode. mm
(26 ih vpaas ,r li-UliUl
. (-27 leell tune «'Urrentur, (mi
023' Vzi cathode iiy-pass . u
(329 HT :ixinotliing condenser ni a

€30! Atrial circlilthl: triluliileir
Ctilr Aerial (lTDliiir lrlflliiig .

u-milm
minim)

l @321 05c. Circuit Lw trackitr . rm ,

. one: usr- rirrnithflVtrimmer n» ma

1 034:. 05c. Circuit LW trimmer n-imm

Clifit Osrillawiiirmiit tuning norm» l

l l
lllcctmlytin. TVnn'abk. tyre-set.

PHILIPS
206A

47

.. Values
IKESIblAr . (ohm)
in V1 irepmrlc CG resistance, .. 470,01)

R15 Y1 heptodc cu accouruiiniz... LINUX)
m; l so ET potential divider l 33 000
R4 Iesistanncs r . ..
1L5 V1 fixed GB mismncn
[hi \1 080. CG resistance .
Jtr' iiicillnmr reaction illtiiipl 3
Rs Vi oscr anode HT feed

1W V2 m decoupling ,.
mo \'2 so HT feed resistance . ow
ltll V2 fixed GR rcslstnlice l 1,
R12 l 1'2 AVC fend potential 2.700.000
E13 l divider resistances l 2,700,COO
R14 Volume control limiter ., 47,000
3715 Manual volume Contrul and

V3 signal diode load ... 500.000
me Y3 pentode no resistance 1,000,000
R17 HT feed IesiEtBlice r 1.300
R18 vs pcntode grid impprr 000

BA!) [vs neutrinos; AVG neiny v} '220
K20 I resistances
R21 VS AVC diode load

Approx.
OTHER COMPONENTS Values
(ohms)
Ll Aerial SW coupling coil 2'0
L2 Acrinl MW coupling cull 23-0
L3 Aerial LW coupling coil 170-0
L4 Aerial SW tuning (mil -1 l
L5 Aerlnl MW tuning coil H) .
Lti Aerinl LVV timing coll 45-0 l
7 IF rclector coil 10-0
LK Oscillator SW reaction (mil 1-!) i
m Oscillator MW reaction coil 2-0
lillJ Oscillator LW reaction coil 250-0
Lil Us rcuit 5W tuning 0011 0-1
L12 ()5 circuit in w tuning coil M
ii: ' ircult LVl'Ituniniz coil 160
L15 Llai IF trlim. W 1
me ~ . . ii) , ,ntnl 7-0
L17 2nd ii trans. my mm ,. 7-u
Liii . sneaker-speeclrrml s i-O l
m - Output llii. 7on0 l
trans. Sec, intui .. 12
_ . Pri., total lili-
r iinrua . Heat-er inc. Very low
trans. Rect. limit. sec, Very low
'1' sen. total 450-
s .511 \annbumls , ches...

513i Mains switchi-

gangedefi 7 J
VALVE ANALYSIS

'lllV( VUlLil-gls mid (rllilclils given in

in mldv nvei'll-ul :ul thaw lillétallliil Ill

Il" rumi-r when ll unis urn-ruling: on

,.

mains- 01'230V. using the 220V tapping on