On Using Higher Capacitance Power Supply Caps

[harry]

Basically when I turn the preamp volume to 7 or 8, with no instrument connected, a very quiet but very horrible high-pitched squealing sound comes from the amp itself... not the speakers, but inside the chassis. Someone suggested it might be one of the filter caps struggling.

Also, the power tubes look weird when this happens. A little grey/blue dot appears on the plate on the top of the anode. I'm guessing this isn't good.

[tedmich]

Also, the power tubes look weird when this happens. A little grey/blue dot appears on the plate on the top of the anode. I'm guessing this isn't good.

did this clean up? Is it possible that you changed the lead dress inadvertently when recapping? Putting AC near the shielded preamp input line can scream badly. I always take a TON of digital photos before ANY work (hindsight I know!) and try to put things back exactly as it was.

Also the caps may need "reforming" if they sat for any length of time (surplus?) as the electrolyte crystallizes on sitting. google "cap reforming" and see:
http://hhscott.com/cc/1st_soft_start.htm
and heres Gerald Weber (Kendrick amps) take:

[tedmich]

can't edit my old post? Sorry about the DRM...here's Geralds book on the google...should be kosher....

http://books.google.com/books?id=fvU...3nAg#PPA238,M1