Studio Pre has low output from one channel?

[red_cahill]

I got a Studio Pre last fall, my first Mesa. I used the output from A first and it sounded thin. It took a while before the "real" sound came in and it came in like a ghost flew into the amp. I knew it had an issue. Took me a while to think of using output B. Output B always works correctly. A is thin and lower output unless I switch from lead mode to rhythm mode and crank bass way up until it pops in again. Then maybe it stays after I switch back to lead and back off the bass, but usually it loses it again. I do have the A/B output pots set identical.

I hope it's a tube. I can tell the reverb tube is almost shot(amp gets a little crackly with reverb). From the symptoms I described does anyone know what's going on or can someone tell me definitely that its a bigger issue than a bad tube? I can replace most components myself, I just can't diagnose very well. Obviously I'd rather not send it off unless its absolutely necessary.

Murphy's Law-- I just tried to get it to do it again so I could be sure how to describe it. It wouldn't do it. A and B are working identically.

Btw--I'm thinking of retubing it entirely now. Any recommendations for brands or specific configurations? Thanks...

 

[Whoopysnorp]

I have had similar problems in my Studio Pre, I think most often on output A. It would do this thing where suddenly the output would gradually (over the course of 5-10 seconds) diminish to almost nothing. My solution has always been to switch to output B, which would always be fine. Sometimes the reverse has happened, and I've had to switch back to output A. I don't remember whether I've ever retubed the entire thing; I've certainly changed V1 and V2, but I don't know about the output tubes. On the other hand, it hasn't done it for a long time now. I'd say retubing is an easy fix that you might as well try. The schematics (easy to find online) tell which tube(s) is/are responsible for the output.

 

[red_cahill]

For what it's worth....found this

http://www.petrucciforum.com/forums/archive/index.php?t-46701.html

It definitely doesn't seem as simple as a re-tube. If I'm going to end up spending $250 or more, I think I'll just find another preamp on ebay and sell the one with issues as-is.