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 Post subject: Rectifier tube arcing
PostPosted: Wed Feb 27, 2013 3:12 am 
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I've got an early 60's croc selmer zodiac 30. It's in otherwise fine working order, tubes are low miles.

I turned it on recently and found the fuse had blown.

Tried a new rectifier tube and saw the rectifier tube arcing and sizzling. Took the amp apart, found one 32/32uf 500 volt electrolytic cap, looks to be of a more recent variety. Bt I've had the amp for almost ten years. Everything else looks clean and unstressed.

Is there any other likely culprit? Or is the cap can my problem?

I did sub in another set of power tubes, and clean the tube sockets. Same result. The tubes light up, but very slowly. When they start getting warm enough to start making sound, that's when the lightning starts in the rectifier bottle.

Thanks for looking

Zack

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PostPosted: Wed Feb 27, 2013 9:48 am 
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Change the rectifier tube and clean it's socket too.

Passive components are rarely the issue. Measure the cap if you can to make sure it checks out.

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PostPosted: Wed Feb 27, 2013 10:31 am 
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I did swap rectifier tube and clean the socket.... Same problem.

Before sputtering and sizzling the amp does take a longer than usual time to warm up to the point where it's ready to make sound.....

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PostPosted: Fri Mar 01, 2013 8:32 pm 
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Worth pulling the rectifier and measuring the AC voltages to see if they are in spec.
If a standby, does it happen Off standby , or on?

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PostPosted: Mon Mar 04, 2013 9:41 pm 
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No standby on this amp. My first thought was that it was a bad rectifier tube . So I bought a new tube Sovtek 5ar4. It arced out too. Took a little longer (as in 30 seconds longer) but it arced out.

So my next thought was the only filter cap in that area a 32uf 32uf @500volt cap. I replaced that with a 50/50 @500v. Put in the new tube and it arced out too.

Removed the rectifier, and all was happy. I put in another rectifier. an old 5v4 i had laying around.. and the amp is operating very happily.

Anyone else have problems with the Sovtek 5ar4? I'm not buying any more of them after that wild goose chase.

Thanks

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PostPosted: Tue Mar 05, 2013 12:00 am 
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Had problems with the JJ version, now I use the Chinese version..

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PostPosted: Tue Mar 05, 2013 11:15 pm 
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Good to know. Thanks!

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PostPosted: Sun Jul 22, 2018 10:08 pm 
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