rocknrolldork said:
MrMarkIII said:
Microphonic tubes will act up, or keep going, even with the guitar volume on zero.
This is exactly what is going on.
Is this a combo or a head? Either way, I find it easier to play with the tubes when the amp is upside-down, sitting on the handle, or on it's side. Trust me on this. It's much easier to see where those #$@&% pins go. The more light you can shine on it, the better.
With a combo, remove the grill, unplug the speaker and take it out of the cab. Then you have a huge hole to reach in from the front. You can set the speaker on the side (now the top) of the cab, and you should be able to plug it back in for testing.
With this weird arrangement, try firing it up (you don't need to plug in a guitar, just turn the volume up a bit), then GENTLY tap on each pre-amp tube with a pencil. Any squealing? That's the bad one.
Start with the first pre-amp tube (the one closest to the input jack).
Have any spare 12AX7s? If you don't have a spare, swap the bad one with the last one (V6). With any luck, you only have one bad tube.
Forgot to ask: Is your amp the DC-2 (Studio Caliber)? Does it have two EL-84 power tubes? Six pre-amp tubes? Two rows of knobs, "Master" for each channel, with an "Output" control?
Here's the manual:
http://www.mesaboogie.com/manuals/Studio%20Cal%20DC-2.pdf
Hope this helps. Seacrest out. :roll: