Philips 821 b service manual

Page 1

TRADER '

11 (Supplement)

SERVICE SHEET

I83

SIMPLE J-Vélht circuit using
Apcntodes throughout is employed in

the chassis of the Philips Szrll bat»
tery operated receiver. It has two aerial
sockets and provision for using both an
extension speaker and a gramophone
pick-up, 0n the long waves a Droitwich
rejector can be brought into circuit bv
means of an extra position on the wave
«hange switch,

CIRCUIT DESCRIPTION

l\\ o altemativc aerial input connections
to coupling coils L2. L3 (MAY. and Liwi).
and coupling condenser 02 (L.\\.), A1,
via series condenser 01, is for distant
reception. and A2, via fixed resistance
BI, is for local station reception. Droitwich
rejector L1. 018 is short-circuited by
switches 51. 32 on M.\\. and normal
L.\\., but a third movement of the wave
t hange switch control opens the switches
and connects the rejector in circuit.

Single tuned circuit L4, L5, 018 precedes
variable~mu pentode radioAfrequency amr

THE WIRELESS TRADER

February 6, 1937

PHILIPS 82|B

3-VALVE BATTERY RECEIVER

DISMANTLING THE SET

Removing Chauizkvlf it is desired :0
remove the chassis from the cabinet,
lirst remove the {our control knobs
(recessed grub screw two in the knob of
the wave-change Vitcli) and than the
[our belts (with washers, rubber washers
ind distance pieces) holding the chassis
to the bottom of the cabinet The
(hassis can now be ulthdriiwn.

To free the chassis entirely, unsoldcr
the speaker leads, and iirhrn refining
ionnect the green lead to the left-hand
tag on the transformer terminal strip
incl the yellou lend to the rightrhand.
Grey lead goes to the tag on the trans-
lormer frame.

Removing Speaker-(Ila remove the
speaker from the cabinet. slacker: the
three clamps (nuts and lock nuts).
When repiecmg. see that the transformer
terminal strip is at the bottom.

COMPONENTS AND VALUES

izrcsrsmxccs

Ri Ania] series resistance
R2 v: gain control
R3
R4
R5 2 g
Rn v; 5.0. HI. teed

7 \2 anode load
Ru V3 c . resistance
R9 H.F. stopper
R lv G n {enlial divider
Ru 3 - > 9"

km on. hzttery load

Approx,

omen COMPONEN'IS Values

l (ohms)

L1 Droitwich njeclorzoil . l 3w

1': lAerirucuupiing coils .. {l :3)

L4 - - . - ., . W '2-5

is }Aemi urctul lumnuiuxls l a
L; } Reaction coils :
f; }vi anode circuit mum..- toils i
- i

Lro V: anode HiF. choke

plifier (v1, mum uranium vrz . . We 1' 5W 5W 1 r ~
Gain control by Variable potentiomctc): __ _ CORD MERE _ , H 1" SP°""" i3: 2 a;
3% \vlisic-i;1 vatrifs 3.8. alppligd apt] also a fimflsfrisscglrligleificr .. 3&5 Sé-SSE }\Vaveband switches .i .. ~
re no: i pu 0 ie va ve s untin . . - - ' ' -
the aerial-earth circuit with cogdenser C55: 8 531%: by. ass ' ' . :3on Sign; fit? $33: 33:31::-
Tuned'mok coupling by L8, L9, cs vi c. .dccoupng i' L 01 5 itswitch
021 between V1 and KI. pentode detector C6 1 Q -C°d°°. .. °'°°°
valve (v2, Mullnrd metalliud BP2)_wIiich 8 gggfigxflg _, ;; 313,5 _ VALVE ANALYSIS _
operates on grid leak system wrth 09 C9 v: gridmndcnscr .. o-poooxa \alvc voltages and currents gum in
.ind R5. Reaction is applied from anode C. V3 55- 3'1 . ' '5 the table (p.111) are those measured in
by mils L8, L7 and controlled by variable a; sz anode Hf. birds/~13 { 3:3, our receiver when it was operating from
condenser 019. Provision for connection cu H,T,supplyrcsrrvoir ., 2~o iI battery reading 138 \' on the HT.
of gramophone pick-up in V2 CG, circuit. EH )1! 0 V3 LF- Coupling - 0:003:3 section, on load. The volume control
Hi1. filtering in anode circuit by choke dz: Dfigfifigfiém, mm 3% was at maximum lint the reaction control
L10 and by-pass condensers 011, 012. Cu: Aerial circuit trimmer moon was at minimum. and there was no Signal
Resistance~capacity coupling by 37, sty AeiflPirCuiHuniDK »» 00 input.
014 and 38 between V2 and pcntode E23; {iffififfigfifimnu 2:33:27 Voltages were measured on the ,Juu \'
output valve (V3. Mallard Pm). Cm Vr anode eircuittuni . l oaou scale ()I an Avnmeti-L rlius, lining
g1}; islziziitainlfgllqum potential divider rvmbie. tlterset. Seati\'t«
. w 101 is
connected in parallel RU)
with loading resistance EMILE W'IP I 591 H I '7
212 across G.B. R7 (Ii 5m m HT ii
battery. Fixed tone
correction in anode
circuit by 015. Pro-
vision lor connection \
of high-impedance ex-
ternal speaker across
primary of internal CM
speaker transformer
T1.
an
Circuit diner-m of
the Philip! 8215.
Not: the alternative CIZ m HI ,
«rill Iockeu. The 3 " -_cu <
Droirwich reieclor 5 i r
i. Iwitched in cix- "0 ii.
cuit in in: fourth " nu»
puiiion or the V G '
wuvechanze letch. in No R
cm B .
a? mi

Page 2

a...

February 6, 1937

Plan view of the chassis. L1 and 018 form
the Droitwich reiector.

AIde; Anode Scmcn Smen :

Voltage Cum-III Voltage Current
(V) ("L-U (V) l lmA)
:33 2-0 I35 l 0.5
.0 ml 50 0-3
135 50 us 0-7

' \'.1l\v In Imr receiver nuikcd I! .

GENERAL NOTES

SWItches. 81-311 arc the u whangv,
llroitwich I'Pjeaor and battery switches,
:nnuctl Ill lhl'ku rotary units wh *h an-
llldlLIltCtl in Ulll IIntlcr-LIquaIs \icn. Thz-
Ilrmns «how thv rlirrrctmm' In which tlII~
Imit< nrr- \II~uI-Il III thI- (1|lele IIn tlllx
[lawn

The t.IlI1I~ lmluw giws the 5\\Ii(.ll
pusItIrnh (or the {our control scttnlg.

\Ull'ung from the fully antirtlnckwisr
pumion

ILW. wnl
CVIiIrII Oil M Vl, l \V. lDrultwicl
met-tor

51 I) t, 0 H

3,; II II I H

q; II II [ II

* I: II II I

II I II II

l) I (J II

II I ( I:

I) I II II

II I I I'

H I' I I

II I I I

Coils. L1 l\ llII- nmiretznwl Inn.
thlc L2-L5 nnIl L8-L9 are in tun at rm-mnl
unit», all (m thr LilIhhL (1er L10 l\ :In
H I". (llUklfi lirfntIllll It" Ih.I\~I~

Scale Lamp. Um I» (I [hlllrh :I.
II'I.\ .\l l. S trin-
Extemal Speaker 'lun makuu .III~

])r()\'l(lt7'l :It the rear Ill the Ih;I.\~I~ tnr (
high rexhtnntn KXt(l'l|({l speaker.
Condensers cm, 013.7 , .

wiper types in II tnhulnr wrunul tlllli
ml the I ll.l\\|\ dek. \I'Ith (onnccting (up
beneath. The tut) tugs close lngnthrl
belong to 010 (0'5 111) and the pzur \\1U\
the large scpnration belong tn 013
(2-0 pF).

THE WIRELESS TRADER

swnth didgrnma.
looking In the
directions of lhc
arrows in the
\Imlrr - Lh355i>
HEW.

Condenser 01.7111!" I- [\IIIdt up I luv
OUOIUI: condensus III parallel

Batteries.~-.-\ 2 V LT. (3011 and a cum-
hinCIl I35 \' Hfl, Ell'fll I) \' C R battery
are recommended.

Battery Leads and Voltages-LT.

cable: Black lend. Lfl. negative; Red
lead, I T pusitu'e 2 V HI and GB.
Cable: Black lcntl, HT. negative and

(Supplement) 111

F. B positive ;] Red lead, H.'1'. pnsm'vc :.
I35 V; Yellow leaxl. HIT, positive I,
135 V if V3 is markcrl \. Izo \' m' nearvfit
If V3 N InnrkCIl ll. Blur luml, (RBI
m: dthf, I, -I (yrepn lend, 2 R.
lltgfltn't _..,\'.

CIRCUIT ALIGNMENT

An Auxiliary IlIul uIll bu nort trimming the Set accurately, SInCc thr
tuning scale [5 not attached to the chassis
Canned up the srt Ith the recommended
battery voltages (sec- General Notes),
ronnect an oscillator to the Al aerial
wicket. and hwllcll «I to l\l.\V.

Turn condenser drive until the 150
Ilcg. mark on the 51: [C Is coincident with
:25 m. Adjust the gain control R2 until
V1 has I5 \' bias, usmg a high rusistancr
\ulunetvr for Incasuiuncnt Turn rmr
lion condenaer 019 to about In ring from
minimum.

C20 should be approximately lluih
mth the insulating 10(1, and 017 about
-I m.m. below. [\mv adjust the two can
llt'lhcrs tor Innximnm output .It .511!
increase reaction until receiver is rm the
\crgi or nerIIaIiIIII. then re-atljnst (:17
,Ind 020.

Check up to sec that: the receiver \\'1]_l
tune to 200 m. and that calibration lies
between the limits marked on the driving
disc at 225. 300, 500, Loco and r,5oo m.

Droitwich Rejecton-Turn gain control
to maximum. Switch receiver to L,\\'..
feed in a 1,500 m.signa1, tune to it: very
accurately. Then adjust 016 Carefully
for minimum output.

Underrclmssis view. The switch units are indicated by arrows and numbers in circles.