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Antique Radio Technical Forum
Cannot see last post--says no page 1964 RCA Radio

Posted by Edd on 03/06/2012 17:07






Sir DAVE . . . . .



FACTOIDS ?

BOX 6 measures 5.5 DC middle FM position...at the AFC there is no voltage.

AM Voltage, same as FM 5.5, no drop.

BLACK BOX 7 set on AM...no voltage.


Well I can live with the first two FM readings . . . for now . . . . but in the sets AM mode there should certainly be power sent up to the AM converter circuitry . . for Q3.


Recheck positioning and see if your perceived BLACK BOX # 7 test point is not really #7 at all ?


Seems like that circuitry concerning the Q1- Q2- Q3 transistors portion, is having its supply voltage being loaded down to ~ 1/2 the specified 9 volts.


That could be due to a faulty Q1-2 or 3 so take DC voltage readings of the CBand E's of those three transistors and pass forward.


Also, we would like to know if those three xstrs seem to be pristine originals, as judged by their solder joints and the brand /type numbers . . . . Sams parts folder gives you clues as to the marked part numbers.


Thasssit . . . . . for now . . .


73's de Edd



At work, put decaf in the coffee maker for 3 weeks. Once everyone has gotten over their caffeine addictions, switch to espresso.






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::Sir David . . . . .
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:: Well, the first thing that you learned was that a mere 1V p/p audio output from of the VCR's audio output is NOT going to punch "speaker" sound thru an unpowered, dormant " 64 RCA ".
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::Now I knew that the VCR had its own isolated switch mode power supply, but was uncertain of any potentially adjunct hummmmmmmm from ground loops, thereby the utilization of series isolation capacitors on both, the shell and center pin of the end of the RCA patch cable
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::Now let me know of any objectionable hum of the VCR audio coming out of the RCA speaker, or is it at least tolerable ?
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::See if the volume control range will let you have all of the volume and sound quality required.
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::With our next consideration, after your just now having confirmed that the power supply and all of the audio amp string is amplifying audio, lets probe the sets RF portion.
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::That is, initially considering that audio from the RCA set is clean enough.
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::To start, since your FM and AM are apparently BOTH inoperative, consult the extreme corner left of your supplied schematic and note that the top portion is the FM portion and it is receiving its switched power supply input from the BLACK BOX 6 reference , at two FM positions.
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::DC meter those voltages presences, while the radio is in either of its two FM positiions.
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::Then, MOVE the knob to its sole AM position and confirm that the prior FM voltage drops off.
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::Move down the schema to the bottom left corner and then note that the AM radio portion there
::is receiving its power in thru the BLACK BOX 7 reference .
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::Confirm presence of that AM voltage only when the mode switch is placed out of either of the sets two FM positions.
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::Standing by for your tests results . . .
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::73's de Edd
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:: Just when you think you've won the rat race . . . DRATS ! . . . . . along come faster rats..
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::::This test is to determine if the radio audio amplifier is working. You should hear the audio from the VCR through the radio. The center pin of the RCA male pin goes though the capacitor to the high side of the radio volume control. The shielded side though a capacitor to the low end of the volume control. If you are not sure the high end or low end, reverse the connections and try again.
::::WE HAVE SOUND FROM THE VCR>>>YEA!! Thanks, now what? Yea!
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:::SOUND...There is a hum (tolerable) Volume is low but controllable by knob (zero to low).
:BOX 6 measures 5.5 DC middle FM position...at the AFC there is no voltage.
:AM Voltage, same as FM 5.5, no drop.
:BLACK BOX 7 set on AM...no voltage.
:What do you think? Thanks---
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IPAddress: ***.162.177.220

Cannot see last post--says no page 1964 RCA Radio 
David 03/01/2012 11:10 
Edd 03/02/2012 19:35 
David 03/02/2012 22:43 
Edd 03/03/2012 12:51 
david 03/05/2012 16:29 
Warren 03/05/2012 19:00 
david 03/05/2012 20:41 
Warren 03/05/2012 21:37 
david 03/05/2012 22:46 
Edd 03/06/2012 00:47 
david 03/06/2012 11:24 
Edd 03/06/2012 17:07 
david 03/06/2012 18:51 
Edd 03/06/2012 23:49 
David 03/07/2012 09:24 
David 03/07/2012 14:03 
David 03/07/2012 14:55 
David 03/08/2012 09:59 

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