Squealing Mark IV

I've been having some problems with my Mark IV. When I crank it up, it squeals uncontrollably. Even when I turn the gain way down it still feeds back like crazy. Does anyone know what the problem could be? I always change my tubes long before they really need to be changed so I don't have much experience with tube failure. I bought the Mark IV used so I don't know how long it has been since it was retubed. Other than the noise problem I’m in love with this amp. I’m actually even thinking about selling my Dual Recto because I never use it anymore. Any help would be really appreciated.

Sounds like a preamp tube has gone bad. You can grab a regular 12ax7 and switch them out one at a time to see if the problem goes away.

pre-amp, probably V1.
ax. :twisted:

I had the same problem with mine.....changed out V1 and V3 (or whatever the first lead gain stage is on).....fixed the problem..

Could be V1 like the fellas mention above. Also, back down on your Treble and Presence settings and see if that helps. My guess right now is the same as the other guys above.

Dale

Granted this thread is pretty old, it also could be the guitar you're using. I doubt it is, but it's worth a shot to make sure the wiring is all correct!

It was the tubes. I retubed it and now it sounds great. So good in fact that I sold my dual rectifier because the Mark IV smokes it in just about every way, and is a lot more versatile.

Here's a high-gain Mark IV clip

http://www.digitalsoundplanet.com/M...p3?PHPSESSID=be52f41bffa7e1600980e9d76b3340e6

Nice clip!