RCA R-74 again

1/18/2009 12:31:56 PMBrett

Pardon my confusion, I know I’ve asked about this before, but… This capacitor pack of 15 caps, are they all electrolytic, none or mixed? I see no indication of them being so but the values would indicate otherwise. See 3-34. http://www.nostalgiaair.org/Resources/712/M0015712.htm
Thanks, Brett

1/18/2009 4:51:28 PMThomas Dermody

Any cap marked with a + is definitely an electrolytic.

1/18/2009 8:21:11 PMBill VA

:Any cap marked with a + is definitely an electrolytic.
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:T.

Brett, they are a mix of caps. No value is indicated on the wiring diagram for them. A wiring diagram allows one to physically trace the circuit and get lost in the maze. You can trace the color wire (except it now is faded) and compare to the schematic ( a bunch of symbols hard to read) and locate the component/connections. Right you are the larger MF caps are electrolytics. And as Thomas says, any with a + is an electrolytic. Except your caps are just buried out of site. Go by the schematic and you will be ok.
Bill

1/20/2009 5:54:25 PMI got all but 1 please help

:Pardon my confusion, I know I’ve asked about this before, but… This capacitor pack of 15 caps, are they all electrolytic, none or mixed? I see no indication of them being so but the values would indicate otherwise. See 3-34. http://www.nostalgiaair.org/Resources/712/M0015712.htm
:Thanks, Brett

I've gotten all but one cap, #C-35. The Red wire goes to the positive of C-36 but doese it go to the (-) or (+) of C-35? I've tried to tell by the schematic but I'm really not sure. I need to go by the color code. Please help and thanks to everyone on this site that helps newbies like me

1/20/2009 7:11:59 PMEdd

With your confirmation of C-36 positive connection having a red wire on it.

Now, the C-35 that you are inquiring about is done the same way, in that its its POSITIVE terminal is receiving the same red wiring, WHILE its NEGATIVE terminal is connected to

a multi juncture, consisting of :

1. . .The center tap of the high voltage winding of the power transformer at the left side of the schema.

2. . .The left side of inductor choke L17.

3. . . The center tap of the filament supply at the bottom.

4. . .The left terminal of the speaker field coil L18.

That is in variance of the C-36 and C-37 companion caps, which have their negative leads connected to ground.

The logic for that is because that juncture is the derivation point of a negative biasing supply voltage that you see routed

from the buss at the very bottom that then flows up and feeds the 1st grid circuitry of your pair of #46 A.F. output toobies.

Now being privy to that special supply situation, recheck your C-38 just to the right of L17 and confirm that it IS installed with its POSITIVE to ground, since it is filtering a further reduced branch of that negative supply that is feeding the 1st grid circuitry of your 56 tube , item #5 .

THASSIT. . . ..

73's de Edd

1/20/2009 7:56:33 PMBrett(70085:70081)

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:With your confirmation of C-36 positive connection having a red wire on it.
:
:Now, the C-35 that you are inquiring about is done the same way, in that its its POSITIVE terminal is receiving the same red wiring, WHILE its NEGATIVE terminal is connected to
:
:a multi juncture, consisting of :
:
:
: 1. . .The center tap of the high voltage winding of the power transformer at the left side of the schema.
:
:2. . .The left side of inductor choke L17.
:
:3. . . The center tap of the filament supply at the bottom.
:
:4. . .The left terminal of the speaker field coil L18.
:
:That is in variance of the C-36 and C-37 companion caps, which have their negative leads connected to ground.
:
:
:
:The logic for that is because that juncture is the derivation point of a negative biasing supply voltage that you see routed
:
:from the buss at the very bottom that then flows up and feeds the 1st grid circuitry of your pair of #46 A.F. output toobies.
:
:
:
:Now being privy to that special supply situation, recheck your C-38 just to the right of L17 and confirm that it IS installed with its POSITIVE to ground, since it is filtering a further reduced branch of that negative supply that is feeding the 1st grid circuitry of your 56 tube , item #5 .
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:THASSIT. . . ..
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:Man, I wish I could understand all of that, but I'm glad I understand enough of it. Thanks Edd
Brett
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:73's de Edd
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1/20/2009 8:12:00 PMBrett C-38?(70088:70081)

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:With your confirmation of C-36 positive connection having a red wire on it.
:
:Now, the C-35 that you are inquiring about is done the same way, in that its its POSITIVE terminal is receiving the same red wiring, WHILE its NEGATIVE terminal is connected to
:
:a multi juncture, consisting of :
:
:
: 1. . .The center tap of the high voltage winding of the power transformer at the left side of the schema.
:
:2. . .The left side of inductor choke L17.
:
:3. . . The center tap of the filament supply at the bottom.
:
:4. . .The left terminal of the speaker field coil L18.
:
:That is in variance of the C-36 and C-37 companion caps, which have their negative leads connected to ground.
:
:
:
:The logic for that is because that juncture is the derivation point of a negative biasing supply voltage that you see routed
:
:from the buss at the very bottom that then flows up and feeds the 1st grid circuitry of your pair of #46 A.F. output toobies.
:
:
:
:Now being privy to that special supply situation, recheck your C-38 just to the right of L17 and confirm that it IS installed with its POSITIVE to ground, since it is filtering a further reduced branch of that negative supply that is feeding the 1st grid circuitry of your 56 tube , item #5 .
:
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:THASSIT. . . ..
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: The C-38 connects to the Black w/red trim wire and the yellow wire. Are you saying the (+) goes to the Black w/red trim and the (-) to Yellow?
Brett
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:73's de Edd
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1/26/2009 4:47:46 PMEdd(70324:70088)

That filter capacitor is the only one that has a polarity deviance from the norm, since it is providing filtering for a negative biasing supply line.

CAP BANK REFERENCING:

73's de Edd

1/30/2009 11:07:20 PMBrett(70541:70324)

:I almost didn't see this. I put it in wrong then. But the radio still works, why is that. I just tested it briefly. Ive been working on the cabinet.
Brett
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:That filter capacitor is the only one that has a polarity deviance from the norm, since it is providing filtering for a negative biasing supply line.
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:CAP BANK REFERENCING:
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:73's de Edd
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