Quality control in Ampeg PF-20T - Nice amp but the buzz...

[agedhorse]

Looks like I mis-spoke about internal accessibility, probably morphed what my amp repair guy told me years ago. My bad.
He was suspecting an intermittent "ultra" filter switch for causing some crackling and the gist was, replacing it would have been more trouble than it was worth. (After an attempt at cleaning didn't work.) He bypassed it & that seemed to help for a while.
Maybe my amp guy was wrong, maybe he's not suited for working on this type of build. If there were anyone else in my area, I'd be all for giving them a shot. (Alas, there isn't. FWIW this guy had a good track record with my vintage Ampeg V-4b, Sunn 200s & Traynor Bass Mate heads, and is well liked by others.)
From my anecdotal perspective, this isn't the only LOUD Technologies product that's given me trouble. My ultimate solution of ditching the offending gear & rolling with a different brand has worked out great for me.
If you have a local person who can properly fix your PF series tube head (or Mackie powered speaker), more power to you.

Replacing that switch on these amps is a 15 minute job, clearly your tech is simply under-qualified. That also assumes that he correctly identified the defect which is also suspect IME based on what you have posted.

 

[Mike Caldwell]

Looks like I mis-spoke about internal accessibility, probably morphed what my amp repair guy told me years ago. My bad.
He was suspecting an intermittent "ultra" filter switch for causing some crackling and the gist was, replacing it would have been more trouble than it was worth. (After an attempt at cleaning didn't work.) He bypassed it & that seemed to help for a while.
Maybe my amp guy was wrong, maybe he's not suited for working on this type of build. If there were anyone else in my area, I'd be all for giving them a shot. (Alas, there isn't. FWIW this guy had a good track record with my vintage Ampeg V-4b, Sunn 200s & Traynor Bass Mate heads, and is well liked by others.)
From my anecdotal perspective, this isn't the only LOUD Technologies product that's given me trouble. My ultimate solution of ditching the offending gear & rolling with a different brand has worked out great for me.
If you have a local person who can properly fix your PF series tube head (or Mackie powered speaker), more power to you.

As mentioned if indeed the switch was/is the issue changing it out would be fairly easy on that amp. Based on the internal posted picture the pots and switches all on the smaller and easy to remove circuit board.
Granted they would need to source the replacement part.

 

[agedhorse]

As mentioned if indeed the switch was/is the issue changing it out would be fairly easy on that amp. Based on the internal posted picture the pots and switches all on the smaller and easy to remove circuit board.
Granted they would need to source the replacement part.

If they were an authorized service center, that would take all of a phone call

 

[S-Bigbottom]

That's what I consider "disposable" construction, not "heirloom". That's okay when the price is reasonable and I get, say 10 years of use from something.

Many forget that in the 70's through the 90's there were more repair shops than now. Amps from that area definitely had issues and needed repairs as often or more than the current "disposable" makes.

For every vintage amp out there still going, there are many more that went into the trash.

 

[beans-on-toast]

An nice repair shop run by an ex-SLM employee. Hit home for more info.

CLASSIC CAR RADIO REPAIR - Our super-equipped shop in Prescott Valley, AZ