First bring-up on 400SII. Caps sizzling?

Jess

Jess

New Around These Parts
Joined
Apr 28, 2019
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Location
Placerville, CA
I just started the bring up procedure for my Rev C Backplanes. Nothing smoked or burned at 60V or 120V and I had voltage at all the test points listed in the documentation. But the capacitors started making a subtle sound similar to a sizzle or boil. Neither of which sound like great descriptors here, lol. I've gone over all my connections more times than I can count but this is my first time doing this so I'm hoping that it's normal.

Jess
 
Jess said:
ah crap. I checked that so many times when I was working in there I thought for sure it was correct :(
Click to expand...

That will make caps sizzle and then explode...how long did you run it that way?
 
Gepetto said:
That will make caps sizzle and then explode...how long did you run it that way?
Click to expand...
At the most a few minutes. I didn't notice it until I was at 120v and was checking voltages on the test points. I brought it back down and then discharged them.
 
Once you fix the polarity problem, I would recommend you bring the AC voltage up to 30VAC, let it sit for a good hour or two, then if OK move to 60VAC, wait an hour or two, if still good move to 90VAC, wait again an hour or two before bringing up to final 120VAC. The reverse voltage damages the oxide layer that the aluminum forms and needs to hopefully reform. Don't do this without being around it, in other words don't walk away from it. Caps can fail catastrophically if damaged.

Before they shipped out to you, they were formed at 90VDC for at least 24 hours to form a good aluminum oxide layer above the normal 80VDC present in a PL400 then followed by a leakage current test. All our caps undergo that forming routine before shipping to customers.
 
The damage may have been done already. Replace them if you plan on running this amp in your house. They can fail prematurely now at any time and you may not be close enough to keep them from damaging anything close. REPLACE and bring yourself piece of mind.
 
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