RCA 16X4

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RCA 16X4

Post by Ed in W. PA on Thu Feb 20, 2014 1:47 pm

Hello,
I am re-capping a RCA 16X4 and cannot tell the voltage rating on some of the paper caps, especially the .05mfd cap across the plate and cathode pins of the 35Z5 rectifier tube. The only cap I have on hand is rated 200 volts, lower than the 160v rating on the electrolytic but I think this cap will see peak to peak voltages not necessarily DC like the filters. Am I correct in thinking this? Could a 200v Orange drop be enough?
Thanks, Ed

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Re: RCA 16X4

Post by Bill Cahill on Thu Feb 20, 2014 2:28 pm

The correct value would be 600 WV dc. I'd use that voltage on all caps.
Much safer that way.

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Re: RCA 16X4

Post by Wildcat445 on Thu Feb 20, 2014 3:27 pm

Some RCA sets used a 1000 volt cap in the output stage. You might keep your eye out for that one. The rest, use 600 volt, like Bill suggested. Good luck.

Welcome to TRF, by the way.

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rca 16x4

Post by Ed in W. PA on Mon Feb 24, 2014 3:44 pm

I finished re-capping this radio, replaced about a dozen caps and about seven resistors. I then brought it up on the variac slowly and found it's performance to be good to excellent. Still I have a few questions, one- the tube lineup was wrong in that there was a 50L6 in place of a 35L6. On a different post I read today (what tube is this?) it was stated that it is ok to leave the 50L6 in as it would put less stress on the filament string, so I left it in. Second question is about the dial string. It seems to drive the vari-cap ok in one direction but not the other. Third question is I would like to have some suggestions on what to clean this corroded chassis with. Two things I have tried so far are Lime-Away and a product called Mr. Metal. They seem to work but won't take the rust spots off. What do you guys use?
Thanks, Ed

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Re: RCA 16X4

Post by Wildcat445 on Mon Feb 24, 2014 4:09 pm

See if you can tighten the tension on the dial string, just a nudge. Don't get carried away, or you will be re-stringing the tuner. That job is just slightly more pleasant than having a root canal without anesthetic, sometimes. You might also sparingly lube the bearings on the tuning capacitor. It it moves too hard, it can make the string slip. There is no specific way to do this, just be careful to not get any lube in the dial string. I usually spray some WD-40 (yeah, I know!) onto a Q-Tip and dab it on easy.

Rust is a problem. There is no BEST way I have found to deal with it. Rust from mouse pee seems to be the worst. It has always appeared to me that each case of rust removal is different from the last. I have resorted to taping off the tuning cap and IF cans and putting the whole chassis, sans tubes and speaker into the beadblast cabinet. Sometimes I scrape and sand, sometimes some kind of rust removing sauce will work. I have also taped things off and sprayed the chassis with silver paint. I try to avoid using steel wool, since the little strands of steel get into speaker magnets and IF cans and can cause lots of problems. Sometimes Scotchbrite on a Dremel tool works well. The guys on here are pretty innovative, and I'll put my money on the fact that someone will chime in here and give you other ideas that will work for you. And good luck.

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WC

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RCA 16X4

Post by Ed in W. PA on Mon Feb 24, 2014 4:38 pm

I tried to tension the dial cord spring a little but with no success.This radio has a bank of pushbuttons across the top of the chassis that looks like a real nightmare to clean and to get them off I will have to take the dial string off anyway. At that time I will remove the vari-cap the clean and lube everything and may try a new dial string. As for the rust spots I guess I will just have to live with them, this radio was in really bad shape cosmedically and I am really glad just to have it playing. The cabinet is in really bad shape as well and I have no idea how to clean it up.
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Re: RCA 16X4

Post by Wildcat445 on Mon Feb 24, 2014 4:46 pm

I forgot to mention about using resin on your dial string. If you know a fiddle player or a pool shooter, they should have some resin for you. Some say wax from an old capacitor works to keep a dial cord from slipping, but I have never tried that. I will try almost anything to keep from restringing a dial. You might also try roughing up the shaft and pulleys with sandpaper or a fingernail file to give it more grip. Good luck.

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RCA 16X4

Post by Ed in W. PA on Mon Feb 24, 2014 5:08 pm

I am glad that you said about using rosin on the dial string. I seem to remember seeing that done when I was a kid, just didn't remember if it worked. I might try the local music shop to see if they have some.
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Re: RCA 16X4

Post by Wildcat445 on Tue Feb 25, 2014 12:34 am

Go shoot a round of pool and steal that little thing they use on the end of the pool cue. Then rub that rosin thingy on your dial string. Maybe the guys shooting pool won't use a cue on you for stealing their rosin. Good luck.  Laughing 

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RCA 16X4

Post by Ed in W. PA on Tue Feb 25, 2014 12:57 am

I was under the impression that the blue cube on the pool table was chalk. I was planning to find a school for young ( or in my case, not so young) girls learning to play violin and hang out there for a while.

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Re: RCA 16X4

Post by 75X11 on Tue Feb 25, 2014 9:41 am

If rosin is refined from pine sap, couldn't it be used in a pinch? I was thinking moisten the string in alcohol and run it across a nearly hard portion of it. I know pine sap is soluble in alcohol. I will have to make a mental note of this.
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RCA 16X4

Post by Ed in W. PA on Tue Feb 25, 2014 9:53 am

I have a bottle of liquid solder flux, I am going to try it.

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RCA 16X4

Post by Ed in W. PA on Tue Feb 25, 2014 10:51 am

The liquid solder flux seems to do the job. Dial cord is now somewhat sticky and drives without slipping at all. I quess time will tell if it's a permanent repair.

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Re: RCA 16X4

Post by Wildcat445 on Tue Feb 25, 2014 1:29 pm

Thanks for the tip.  I'm glad you got it fixed.

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