Ampeg BA115HPT: fuzz on note decay

[jazzido]

Hello everyone,

My Ampeg BA115HPT has started to show a really nasty fuzz that's more noticeable when the note starts to decay.

From what I've read on this forum, that is usually a sign of a bias problem. Strangely, the problem doesn't appear if I apply a signal to the CD Input, that is directly connected to the power section, so I doubt that I'm dealing with a bias problem.

Since the first time the problem started, there's been a couple times where it just didn't happen, adding mystery to the story.

Anyway, I took the amp to a local technician. He first told me that the tube was microphonic, replaced it, but the problem was still there. Then he replaced the bias trimpot, suspecting an issue there, and told me that the amp was ready to go. Took it back home, plugged it and it only lasted less than a minute before it died (fuse?).

The amp is back at the technician's shop, and I'm starting to doubt his abilities.

Any suggestions?

Thanks!

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jazzido