Belmont Radio Corp. A-7AF21 Schematic

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Manufacturer:Belmont Radio Corp.
Description:SERIES A

Schematics Content:

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Page 1:


U E:E_.EE :__v <.NO SSE m 1:a .IB E9; .
mio... 12?? .__ gum :2_1 Eu.: @5216 of _u :o__BE _?1 *a 'm1' 1:2 22:
. . SEE m 1:.~ o>o._u_E
`<29.. _2.:22 0mm 50:20 u_+qu+:< urn? m om 1_:27 .>o_> M320 mum :otu>:o0 wr . . mn

?J0hn F. Rider

Page 2:


Series A


No alignmenf of ihe FM seciion of ihis radio should be
ai'iemp'ied unless you are posii'ive ihai* ihe circui'ls are in
need of adiusimeni and you have *he necessary equip-

All componenis used in 'ihis radio are ex'fremely slable
and ihe iuned circuiis should require no adiusimeni
over a long period of +ime.


FM Band Secfion l. F. and R. F.

Bond Swifch in FM Posifion. Dummy Anfenno .1 Mfd.


The following alignmeni' is based on ihe use of ihe new
Simpson vacuum 'iube volimeier which has a "'flcaiing
ground". In oiher wordsI ihe mei'er, when used as a
vacuum +ube voll'meierl can have boih 'ihe pcsii'ive and
negaiive sides connecied io poinis above ground and
si'ill give frue readings.

A siandard AM signal genera'ior is required.

GENERATOR 'gamsylg'l Mimi coNNEcrloN 'Tlgn?sg'mgis Amusr Fon
10.7 Mc. P- _ 1 P- UAL BoHom Core Resonance
Use aboui olfn1r;gub m gint; ? :rims 5 Primary of T9 should be abou*
10.7 Mc. Pin N?_ 1 Top Core Zero. Use zero
Use aboui o_f 12AU5 See nofe "A" Secondary of T9 cenier scale
.1 voir Raiio De'ieci'or See noie "B"
10.7 Mc. - . Primary and Secondary Resonance
use abour 330 TFSQAQ P'" NZ' ? ?i. 'ZH-5 of T7. FM Driver IF should be sbour
microvolis a" minus See chassis view. 3 volis
microvcli's a" m'nus See chassis view. 3 volis


NOTE "A"-Conned iwo resisiorx in series, IOOK OHMS eachI
from Pin No. 7 of |2AL5 io B minus (pin no. 5). These resisiors
musf be maiched wii'hin 5%. Conneci' vacuum iube velimeiar be-
iween `ihe midpoinf of #he rasisIors and poin'l' n.

NOTE "B"-li T9 has been Tempered wiih, ii is possible ihai no
crossover poinr will be found aI iirs'I. Careful adiusimenI of boih
primary and secondary is necessary.

Check poinfer so #haf fhe righf hand edge of fhe poinfer skirf coincides wifh #he
righf hand edge of dial marker af fhe exheme lighf when gang is closed.
For Adiusfmenf, see dial mechanism i//ushafiom

NOTE "C"-To use a VTVM which does noi have 4ihe "floeling
ground" feaiure, in siep 2 above, conneci "ground" side oi VTVM
+o midpoinr a; mmm (Noie "A") and "high" sid. io poinf a.
GENERAL-Inpui signals should be adiusied Io give approximaiely
3 volIs. The raiio deiecior is operaiing af a reasonable level ai
'ihis poini and will give ,he 'frues'r indicaiion of correct alignmeni
wifi. n... procedure spmmd.

$2552.22? mmm ro RADIO ""1"" coNNEcrloNs
Marker ferminals 'For maximum
S N 8| Pin No. 7 of
Tune in ee de I' I FM Mixer CZ-C 12Al-519 B minus
98 Mc' Gen. Signal helm" 'For maximum

NOTE "A"-|i a signal generaior wiIh ihe above fundameni'al ireA
quency is no'r available, if is some'imes possible ie use harmonics.
Use exirerne care in picking harmonics. An aliernaie procedure is
Yo use a local siaiion carrier of lrnown frequency ie align Ihe FM
Band and io use 'Ihe vacuum hibe veil-mehr as above for resonance

indicaiion. A weak carrier, however, will noi produce 3 volis.

NOTE "8"-Cnnneci 300 ohms in series wiNI "hai" side of gener-
aior and conneci' `Io lofi hand screw of exIernal FM Anienna TerY
minals. Canned cold side of generafor Io righi hand screw.

o John F. Rider

Page 3:

Series A



:_ was ,223 2 __; __ E _ 5 .

.o_me-m wo :cruel _2m 2_sz m :wwfwm _3113 _vm2_.(R)m.0 tam _5252.3 *EE oo. "vaZ

.?351 wo 222; SEE m o* 2:22 E "wHOZ


a John F.

Page 4:


MODEL A-7AF21,Ser~ies A

GENERAL-A dual 'track drum pulley and fwo indivi~
dual cords are used on Ihis model.

The rear 'Irack carries *he Drive Shing (see Fig. I
and 2) while #he fronIh Iracl: carries Ihe PoinI'er Shing
(see Fig. 3 and 4).

DRIVE STRING: Using approxima'fely 20 inches of dial
cord. fusion one end fo Ihe Iension spring and pass
around drum and drive shall` (Fig. 1). Con+inue cord
around drum and pass Ihrough hole in rear #rack (see
Fig. 2). Tie end ol cord Io spring so I'hai' spring is ex-

POINTER STRING: Use approximalely 40 inches of dial
cord, fasi'en one end +o fension spring and pass around
drum pulley (see Fig. 3). Confinua cord (Fig. 4) from
poin+ B around idler pulleys, around druml Ihen pass
'Ihrough hole in fron* Irack. and I'ie cord Io Iension
spring so fha# Ihe spring is exl'ended '/4 inch.

POINTER CALIRRATION: Adiusi' poinI'er as shown in
Fig. I4, Ihen loop PoinIer sI'ring once around uprighi' ear

and Alignmenf

will. an; mg! drum mmm oomolelely

WTS ownler olooumoo lm: up me loll mg!
on PDinhr carriage. ol'h' pow-'ummm am shown mm]
(UNDENSERS Tl Loop lnhnrla I
cl.Asco a.sA.lesoz 4 muon gong "new" l 12,|3.l4 RF ollolo a
cz.Aac Trlmmor on gong a. AM om ooil l
cs,1,0,ll,|z, A-selzm .005 mi. disk coromlo I2 11 B-lalmwoo FM dnvor lF l
43A; T9 B-lsM-lml FM folio doloolof l
club v<>sln_lo71o .05 mf, 200 vom, pop" z m AMA-um RF ohol. l
G23 c-ac-lwxa s mf x loo vom. .loolrolylio | IIIIIL PARIS
cu c.el=a.|| aao mmf. mio. l Momma Di., md, |
6163118.30 C-BG-l |732 470 mmf. coromio l A.3A.|5504 Tuning ,5.9 |
caz c-se-lazol |000 mmf. coromlo | ll-29c.lsevo "c'wosllof for obo" |
cannon A-ee-maz_| 40-20-20 ml. soo volh. oloolrolylm, 546467,., Dill Pain," I
20 mf x 25 "I" I A-ssA-lovev Dill ming so" roq. yd
cm c-aD-lml .Iz mf. 200 volh. pup" _ I4.-40A-l007s Tonsion spring 2
c44 A-sC-lmo w mf x |20 volls. ulechIyI-c I BAM-lsvla-l Dlol .ool- broom 2
m A455466" SupprBN.. | B-ZOI'I6988 Type 932 Record Changer. (Ihru
R5.6.e.|2.|9 c-val-ss 410 o m., 2 won s
R7.l| oval-43' ss ohms. 1/1on z MISCELLANEOUS
Rla mal-79 27K ohms. '/2 vm I Msn-|3420 Ml". 9 pin who mm 2
Rls,40 mal-33 2.2 mgchmf. '/o "If 2 A-lsc_|6291 Mir.. 1 pin lub. .ookof 4
Rls CMI-34 2.2 megohms V2 wa" I ,445040440 oolol moo soolof l
RI7 C-9BI-54 220 m-svhms. '/z "N I A-amlom Tuning 'hon booking l
Rla c-9BI-w 680 moquu-ns. 'A on I Ama-|3050 FM alpolo Torminol ship l
R20 A-loA-lbsoa I mqgohm. volum- mlm' and MLA-|6120 Pllof ln. ommbly l
Rzl c-vBI-Sb M magohm. '/1 "II I A-lvs-lzlm Phono pickup .ook-l l
R26." C-9III-27 220K 0M" '/z "I+ 2 msn-|0075 small lylio mlg. plolo 1
RZB.36 C-9C4-50 |00 ohms. 2 warts 2 3.55.1583." Knab 3
R29.30 0954-62 |000 ohms. Z wall; Z 3.5545154241 Knob win, dcf |
R31." C-9B4-55 |800 ohms. 2 walh 1 A.23A.|0344 Lin, cmd lock |
a-l4M-ll47v-z Lino :ora l

?John F. Rider

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