• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

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

Mark Ellis

Mark Ellis

Dec 25, 2017
143
157
Sydney Australia
#1
I have a Ampeg PF-20T coupled with a 15" EV TL606 speaker. This is a great amp in the studio and practice room. Just a good reliable vintage sound.

There is no fan so it is very quite, or it was until it started buzzing. I traced the buzz to mechanical noise from the power transformer.
The work around for it has been to anchor the metal covers for the transformer windings into place with ice-cream sticks and rubber bands. Now they don't buzz.

I should get around to opening the transformer and gluing the covers down with epoxy but Ampeg should have had better quality control.

While this fault is annoying, if this amp was lost of stolen I would buy another or a Ampeg PF-50T without hesitation.

Bass amp.jpg


Bass Head.jpg
 
  • Like
Reactions: Jefenator and el jeffe bass
#8
Inventive!

I would slightly loosen the four chassis mounting bolts, then retighten them in an X pattern. This could relieve any mechanical torsional stress on the transformer's frame and fix the issue. Since the elastic brace works, try leaving it on while doing this.
 
Last edited:
  • Like
Reactions: MattZilla
#10
Mark Ellis said:
I think I am way outside the warranty period. I expect this type of product to last decades and perhaps, with careful maintenance, a century. There are amps from the 50's and 60's still in people's studios today, why not this?
Click to expand...
The vintage tube amps I've had have all been very friendly for my tech to work on. Easy to get in, source & swap whatever was needed.
My PF-50T was not like that at all. The internal construction was very cramped, would have taken my tech an awful lot of [expensive shop] time to dig in deep enough to get to the board where some switches were mounted. And the part was unique to that amp, not so easy to source.
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. My PF-50T was disappointing in that regard.
I think I got a lemon; many other users seem to have been luckier. Even so, based on my experiences I can't recommend this series for the quality of construction. For longevity, I would suggest restoring a vintage amp, or spending a few extra $$$ on a newer hand-built one.
At least your issue seems to be out in the open. Fingers crossed you can re-mount or permanently brace that transformer with relative ease.
 
  • Like
Reactions: KevInDaBassment
#12
Jefenator said:
The vintage tube amps I've had have all been very friendly for my tech to work on. Easy to get in, source & swap whatever was needed.
My PF-50T was not like that at all. The internal construction was very cramped, would have taken my tech an awful lot of [expensive shop] time to dig in deep enough to get to the board where some switches were mounted. And the part was unique to that amp, not so easy to source.
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. My PF-50T was disappointing in that regard.
I think I got a lemon; many other users seem to have been luckier. Even so, based on my experiences I can't recommend this series for the quality of construction. For longevity, I would suggest restoring a vintage amp, or spending a few extra $$$ on a newer hand-built one.
At least your issue seems to be out in the open. Fingers crossed you can re-mount or permanently brace that transformer with relative ease.
Click to expand...

This is only because you (obviously) have no experience working on electronics.

There is nothing an experienced and truly qualified tech couldn't access in less than 5 minutes on that amp. From a technical perspective, it's one of the easiest tube amps to work on that I have ever seen. Far more service friendly than most vintage tube amps actually.
 
  • Like
Reactions: keyofnight, S-Bigbottom, ColdEye and 2 others
#14
cdwthunderfoot said:
Through hole components with reasonably defined, easy to follow traces. I would take that any day over the Double sided,densely populated SMD boards I used to work on.
Click to expand...
Or a boutique point to point rats nest build... ;)
 
  • Like
Reactions: keyofnight, S-Bigbottom and MHensleyJr
#15
I can't speak to reliability from new; I bought my PF50T used so take this with a grain of salt. I had to perform the "hum fix" the factory solution for which is still unseen, I've had a preamp tube fail, and the DI has been too noisy for a recording studio since I got it. A few months ago it finally gave out altogether. I even bought a Quilter Base Block to connect for louder gigs and such. Fortunately, the Quilter sounds great on it's own with my cabinets.

Like I said, the PF50T was used. But it was also in extremely nice shape, packaged very well, and looked to have been cared for. If it was stolen I don't know if I'd buy the same amp again.
 
  • Like
Reactions: Jefenator
#16
Mark Ellis said:
I am surprised no-one from Ampeg has picked up on this thread. It is a simple quality control failure. Has anyone else had this problem? How did you fix it?
Click to expand...
I know somebody has addressed this with a relatively simple modification in a thread. A search would probably give you what you seek.

For what it's worth, I have a PF-50T that I have owned for a few years without any noise issues. The only issues I have had with that amp are that the speaker connector in the 1x15 cab was loose when I bought it, and I had to replace a preamp tube after a couple years.

tchristian said:
If it was stolen I don't know if I'd buy the same amp again.
Click to expand...
For typical used price, I would agree. I was extremely lucky to get mine for $250 at the Bass Club in Chicago in 2019. That was $250 for the combo-- PF-50T and 115HE. I thought the guy misspoke when he told me how much he wanted for it.

I asked what was wrong with it. He said he'd simply been trying to move it for a very long time, but since the vast majority of his business is online, and because he didn't want to pay the shipping cost for an 80lb combo, his only opportunity to sell it was the relatively few walk-in customers he got. I might have mentioned that I was on a trip for my birthday weekend, too.
 
  • Like
Reactions: tchristian
#20
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.
 

Latest posts

Top Bottom
Back