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#1 2012-04-09 15:38:55

New member
Registered: 2012-04-09
Posts: 1

Early 70s VT40 - unwanted distortion/muffled signal??


I've recently purchased a "fixer upper" early top-loader VT40 that I knew had some problems, but the price was right, so I had some wiggle room to get it fixed.

Originally, the amp had a few problems. (1) Seemed the volume pot on the bright channel was shot, (2) there was a bad hum when switching the "ultra-high" rocker (got worse if it was on), (3) and after warming up for about 10 mins it seemed like the signal would start to distort or muffle a bit.

I've got a buddy of mine that works on these with good success, and we replaced all the speakers, fixed the volume pot problem, and the hum.
We thought we were good to go, but it seems the distortion/muffled signal problem is still there.
(also now, the volume pot on the standard channel has now broken, but that's another thing:S)
The amp sounds incredible after taking it off standby and playing for 10mins, but then it starts to "fizz out" a bit. For instance, if I play a single note, its almost as if the note has  good attack but then the signal is quickly squashed, like compressed or something, and distorts a bit.
The amp still seems plenty loud - this problem is evident at real low volumes.

Preamp tubes seems maybe the most likely candidate, so I'm looking to change those out one by one on the working (bright) channel side.
If that doesn't work though, any ideas?

Thanks a lot!



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