Gamble-Skogmo, Inc. 05RA1-43-7755B Schematic

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Product Information:
Model:05RA1-43-7755B
Manufacturer:Gamble-Skogmo, Inc. (Coronado)

Schematics Content:

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Page 1:

GAMBLE-SKOGMO PAGE 21-7
GENERAL DESCRIPTION '
This radio is an 8 tube (including rectifier tube) AC receiver with
automatic record changer, designed for reception of stations in the
standard broadcast band between 540 and 1600 kilocycles and FM (Fre-
quency Modulation) stations in the FM Band of 88-108 megacycles.
Controls are provided on the front panel for tuning, tone, volume and
band or phono selection. Special features include two built-in antennas,
a grounded grid R-F amplifier stage on the FM Band, automatic volume
control, compensator circuits to prevent oscillator drift, beam power
output stage, permanent magnet dynamic speaker and an electrostatic
shield in the power transformer to reduce power line noise.
MODELS O5RAl-H3Q755A,
ELECTRICAL
SPECIFICATIONS
Power Consumption
117 volts AC-G0 cycles 40 Watts
60 watts phono operating
Power Output -
1_5 watts maximum
.8 watts 10% distortion
Speaker-8" PM dynamic
Frequency Ranges ~
Broadcast 540-1600 KC
Frequency modulation 88-108 MC
Intermediate Frequency -
Selectivity - AM - 45 KC broad
at 1000 times signal, measured
LF. FM-200 KC broad at 2 times
down
LF. FM - 950 KC broad at 200
times down
AM Sensitivity-(For ,5 watt output
with external antenna)
25 microvolts average
FM Sensitivity-(For .5 watt output)
25 microvolts average
GBE6 MAI/ GAVE 6V6GT
Tube and p;,,| Lump 1 esac AM gnigrterfa FM osc. V A6 i, ?_6ALS A `
c?"'P'?"'?"' 1 GBA6 2nd LF Amplifier i ` 1 , <-zsrsv
1 6AL5 FM Discriminator I rf
1 GAV6 Audio Amplifier, '
AM zmi Detector and Avc W PHONO . (C)
1 6V6GT Audio Output MOTOR/'"" ._2m
1 6X5GT Rectifier
l 12AT7 R-F Amplifier & Mixer
2 No, 47 Dial Lamps
n|voL? ANTENNA 5?C""
POINTER CLAMP
DRIVE CORD REPLACEMENT
Replacement of the drive cord may be accomplished as Dm* BRACKET
shown in the illustration. For this purpose use the new
drive cord assembly listed in the Replacement Parts List. I
Turn the gang condenser until the plates are fully meshed. n|AL_ STRING " "
Then install the string as shown, winding three turns
clockwise around the tuning shaft with the turns progress- gm/?1
ing away from the chassis. After the cord is installed, _ GANG CONDENSER
rotate the tuning shaft several times in order to take up = ,,_,,,,, ;~o;%?; CLOSED
any slack in the cord.
ins I ll 1-
(C).Tohn F. Rider

Page 2:

PAGE 21-8 GAMBLE-SKOGMO
ALIGNMENT PROCEDURES
The following is required tar aligning:
An All Wave Signal Generator Which Will Provide an Accurately
Calibrated Signal at the Test Frequencies as Listed.
Volume Control Maximum all Adiustments.
Connect Radio Chassis to Ground Past of Signal Generator with a
Short Heavy lead.
Allow Chassis and Signal Generator to "Heat Up" for Saveral'
Output Indicating Meter, Nan-Metallic Screwdriver, Dummy Antennas
- .1 mfr and 50mmf. Minutes,
SIGIIAI. GENERATOR
CONNECT THROUGH CONNECT GANG
FREQUENCY GENERATOR DUMMY GROUND CONDENSER ADJUST ADJUST
SETTING OUTPUT T0 ANTENNA TO SETTING FOR
455 KC Control Grid .l mf Chassis Rotor Fully Open 2nd |.F. Pri. (I) Maximum
lst 611.46 Pin No, 1 Base errd Sec. (2) Ovttwf
455 KC cerrtrel Grid .1 mf Chassis Reter Fully Open lrr l.F. Pri. <:l> errel Maximum
6BE6 Pin No. 7 Base Sec. (4) OUIPUI
455 KC Control G.-;,,| .I rr-it Chassis Relrrrr Fully 2rrd I-F Pri. (1) Mexirrrum
ease Pirr Ne. 7 Base Open errd see. <21 Output
1620 KC Cerrlrol Grid -l mf Chmsis Rotor Fully Open Ossillator C-A1 Maximum
ease Pin Ne. 7 Buss 0\>>1Pv*
1400 KC External 50 mmf Chassis Turrr Rotor to Max. Output. Antenna C~2 Maximum
Antenna Lead Bm Set Pointer to 1400 KC outpvr
See Nele A
NOTE A-It the pointer is not at 1400 KC on the dial, reset painter te the 1400 KC mark on the dial scale.
The following is required fer aligning:
FM STAGES
An accurately calibrated signal eerrererer providing urrmerlrr-
lated signals at the test frequencies listed below.
Dummy Antennas and I-F Loading Resistor-2500 mmf, 300 ohms
Zera eerrrer scale nc yerrrrrrrr rulre yelrrrreler lreyirre e range ei
<11 rr zero center scale meter is rrer available, e standard scale
weerrrrrrr mee yelrrrreler may be used by rererrirre the meter tonnes-
rrerrr for negative reerlirrgrr.
Allow chassis and signal gerrererer to "meet up" tar several mimrree
SIGNAL GENERATOR
CONNECT THROUGH emo GANG
FREQUENCY GENERATOR DUMMV SWITCH CONDENSER Amusr rmlusr
_ SETTING OUTPUT ro ANTENNA SETTING SETTING g Fon _
mrerimirreter 10.7 Mc .sails zrrri l>>F 2500 mmf FM lleler Fully Dire. Pri. <51 M.,,.;,,..r,r.
Pirr 1 erra clrereir Open Note A nenurrer.
10.7 Mc one zrrri l-F 2500 mmf FM Rotor Fully Dire. ser. <61
Pirr 1 rerra Chassis Open _ Note B
I~F 10.7 Mc 6BA6 let l.F 2500 mmf FM Rater Fully zrrrl l>>F Pri. <71 Maximum
Nate c Parr 1 erre Chassis overt ser. Note 0 neneerterr
niserimirrerer 10.7 Mc asm Ist l.F 2500 rrrmf FM Rotor Frrlly Disc, Pri. <53 Merrrrrmrrr'
Pirr 1 errd Chassis _ _ operr Nere D Deflection
l_F 10.7 Mc Junction C-:ln re s 2500 mmf FM Rotor Fully lst IYF Pri. <91 Maximum
(Dual 100 mmf eerie.) Open ar see. (10) Deflection
Arre chassis zrrd l-F Pri, <71
In Order slrewrr
_ A __ _ ___ Note 0 *
10.7 Mc Same as ebeye 2500 rrrrrrf FM lzerer Fully Disc, see. <51 Merrirrrum
orrerr Nele B Deflection
RECHECK 1-F ADJUSTMENTS IN ORDER Given
Oscillator 10s.s Disconnect built-in rlipele err. :loo alum FM Rotor Fully oer. c.25 Merrirrrum
lerrrre and eerrrreet generator oeerr Dnnection
re aieele rermirrele warn re.
sister ir. reriee.
r Antenna l0f.5 Same as above 300 rlrrrrs FM 'rurre rerer fer Am. c-39 Maximum
mer.. Avc voltage Detleerierr
ltscllscx ANTENNA a. csc. ADJUSTMENTS IN ORDER GIVEN
FM ALIGNMENT NOTES
NOTE A-The zero center scale DC vacuum tube voltmete
connected between chassis ground and the AVC line.
A signal of .I volt must be ted into the re
ceiver fer
Nate output voltage on the zero :enter oc vacuum
NOTE B-Disconnect :era center DC vacuum tube voltm
AVC and tanned it at tire audio takeoff poi
eter from
nt at the
27 K ol-lm resistor (R-10) and its junction with the terminal
strip. Adiuxt for zero valtage indication.
Nor: ceilM l.F coils rrruir be aligned before attempting to eligrr
Nora 0~c-errrreri rere center oc yeruum tube yelrrrreler as in Nate
A. Aeirrsr irrpur to eirre rrrrrre output an llre rere center oc
yerrrrrm ruler- valtmeter as in Note A.
(C)John F. Rider

Page 3:

GAMBLE-SKOGMO PAGE 21-9
MODELS OERAl-L3 -7755A,
* "if \ f and ?
(C)John F. Rider

Page 4:

PAGE 21 -1 0 GAMBLE-SKOGMO
MODELS 0 SRAl -L13 - 775511
REPLACEMENT PARTS LIST I
Rel. NG. DESCRIPTION Puri Nc. Ref. No. DESCRIPTION Puri Nl.
CAPACITORS R-13 I
11.191 Resisior, corbon; 470 K ohms 0.5 w _BB5474
c.1 Gang Condensef Assembly __ 144209 11.24
c.4 11.21 vohnno Control 0 Swilch; .5 rnogohrn .s6x372
C>>5 11-23 Tone con1ro1, 3 mo ohms ____..._,. _40x2a5
C-10| me Resisior, corbon, azo ohms 2,0 w ._ _0a4s21
C-lI| Capacitor, corornao; 5000 nnnf _47x5o7 11.29 Resislor, corbon; 1 me ohm 0_5 w ?85105
C-17| 11.30 Resistor, Carbon 270 ohm, 0.5 w ,_ .ss4271
Q12 1 TRANSFORMERS AND COILS
CM, 1.1 chonro, Insulated .______,..,..._,,_ ___:1545
6_1 M 1>>or1 61 1.4 (Znd 1.1 Trans. FM) L-2 chouro, Parasitic __ 042103
Cam Copomor, Ceron11?; 220 mmf ....._,. .A7XA68 1.4 ghd 1.1= rrono. (FM) _9A206l
c-21 copooieor, Dry E1oozro|y11?_ 5 mf 100 v. _45x361 V5 7"" "F T'?"'~ (AM) -->>- -M2063
UM Cupccnor, corornn. 2,2 mmf 1,____ _47x557 1,7 0,?;,|?,,,,, can (AM, ____ _oA20?5
CMA; 20 mf ,OV 1.12 Antenna Co1| (FM) __ 3.42066
c-200 1 Cnpuciior; Dry sloofroivqar; AO mi 150 v .,__ 45x:160
c.5o copoonor, Mowers Mica; :130 rrnnf __ _47x470 D|A|- AND TUN|NG PARTS
0328" 'copoonon Dual coronnr; 100 rnrnf _ __.76x4 1>11o1 ugh1 sor1ro1 4>>on111|y _._,_.. __7A199
039, Condenser coohaon 511111 _. _20)(2b0
C_A] ' Perl of C-1 (Gang Condenser) Drive shun ,______ ___4_, _ 26x486
Dial Glass _.,____.....__ _53X732
RESISTORS
R-1 Resisfor, corbon; 47 ohms 0.5 w _. _sa5470 M|5??L|_ANEg|_|?
11-3) Resinor, corbon; 1000 ohms 0_5 w _ _B85102 Band chongo Switch _.__ __.___. _____.. _ _ 24395
R_Bs Reslsfor, Carbon, 68 ohms 0.5 W _ _ _ _B84bB0 Tube Ssckey (IS, 6BA6) _ I A H -v3A426
R-5 I Tube so=1ro1 160261 ._.___ ,,__ 3 A227
:gi Resisvor, corbon, 6800 ohnro 0.5 w __ 1384681 Tube Socket, Mouaod (Ocful) __.5A235
- robe Socket _.__. __3A439
S`;5? Resiskof, Carbon; A7 K ohms 0.5 w .aa547z M" 5??'f?' (UAW) ""> -~3""3
' _ Knob (Tumng) ...___._ _, _\0A699
11.9 Resnstor, cofbon. 2200 ohrno 0_5 w _ss5222 Knob ,logon
11.10 Resistor, corborn 27 1< ohms 0.5 w _ 005273 Knob mono) _.,____ 402701
11-11 Resistor, warewouna; 3.6 ohrno 0_5 w _43x2;13 Knob (FM-BC-PH! ____,__ 40,1702
Rfu' nzoomor, Carbon; 100 K ohms 0.5 w _ 005104 s"??"?" 8" """` ?>"~'--- -'YM77
, Record fhongo-r~5 speed 204166
11.15 11o?1=1or, corbon, 22 K ohms 0.5 w _ _ssszza line Cord 0 Plug Aorornbry _.__ ,1;1X5.,6
1117 nooaofor, Carbon; 220 ohms 0.5 w ,BB422I Line Cord clornp _ __..__._. _30X5..,0
(C)John F. Rider

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