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  #31  
Old 01-15-2017, 11:44 PM
Phil Nelson's Avatar
Phil Nelson Phil Nelson is offline
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Well, the doorknob cap was bad, after all. When I played the set to check another issue, a faint tick-tick returned in the HV section and then the cap failed, causing hash in the video and loud static in the audio. When I swapped in a doorknob borrowed from my National TV-7W (which has four to choose from), the picture stabilized.



I don't have a cap checker that can test at such high voltage, but out of curiosity I temporarily clipped the old doorknob cap in parallel with the good one. It immediately started hissing, so I guess it really is a goner.



There's more work to do on this set, but I'm counting this problem resolved. Thanks again for the good advice.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Last edited by Phil Nelson; 01-16-2017 at 08:58 PM.
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  #32  
Old 01-17-2017, 11:05 PM
EdKozk2 EdKozk2 is offline
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Phil,
How did you get that chassis so clean looking, it almost looks new.
Ed

Last edited by EdKozk2; 01-18-2017 at 12:18 AM. Reason: spelling
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  #33  
Old 01-17-2017, 11:54 PM
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Phil Nelson Phil Nelson is offline
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Both chassis on this set had bad rust. After using Naval Jelly & the usual tomfoolery, this chassis still looked rotten, so I painted it (not my usual practice).

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
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  #34  
Old 01-18-2017, 12:17 AM
EdKozk2 EdKozk2 is offline
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Better than having rust.
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  #35  
Old 01-18-2017, 10:56 PM
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Penthode Penthode is offline
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Nice job
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  #36  
Old 09-16-2020, 11:44 AM
Resonance1 Resonance1 is offline
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Need replacement for DuMont 20D-4901-2 vertical blocking transformer

I have the same problem. Anybody have any idea where I can find a replacement? Playthings of Past is currently "down" while the new owner tries to organize all the stuff he purchased from Gary. Is there any way to use two transformers or otherwise to re-engineer the circuit?
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