Hey guys, I have a problem with my Mark IV, hope you guys can help:
Whenever I start the amp, my lead channel is fine, but after a couple of minutes playing, the volume and the gain drops. I leave it alone for a couple of minutes, then the volume and gain goes back to normal, then goes down again after a couple of minutes. This happens to when I switch to Lead channel from Rhy1 or Rhy2 channel.
I don't have a problem with my Rhy1 and Rhy2 channels.
Is this a tube problem? I googled, and read that I should swap my V3 & V4 tubes. I did that already, but am still experiencing the same problem.
Any ideas?
Thanks!