Belmont Radio Corp. A-7AF21 Schematic

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Product Information:
Model:A-7AF21
Manufacturer:Belmont Radio Corp.
Description:SERIES A

Schematics Content:

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Page 1:

VBELMONT PAGE 20-1

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:

PAGE 20-2 BELMONT

MODEL A-YAFZl,
Series A

IMPORTANT

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.

ALIGNMENT PROCEDURE

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

FM-|.F. ALIGNMENT
Bond Swifch in FM Posifion. Dummy Anfenno .1 Mfd.

NOTE

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.

SIGNAL VACUUM TUBE VULT
GENERATOR 'gamsylg'l Mimi coNNEcrloN 'Tlgn?sg'mgis Amusr Fon
FREQUENCY T0 RADIO
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

NOTES ON FM-l. F. ALIGNMENT

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.

FM-R. F. ALIGNMENT
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.

SIGNAL
CONNECTION V '|' V M
$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

BELMONT PAGE 20-3
MOD

fig

:_ 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

Rider

a John F.

Page 4:

PAGE 20-4 BELMONTA

MODEL A-7AF21,Ser~ies A
REPLACEMENT 0F DIAL (ORDS

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]
REPLACEMENT PARTS LIST
CDILS AND TRANSFORMERS
(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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