solo button stops working when amp warms up

myoung2746 · May 15, 2011

Hi, I have a rectoverb 50 combo amp. The solo button on the footswitch works fine whenver you are first starting out playing.
After you have played for at least 30 minutes, (the amp is now a lot warmer) the solo button stops working (light still comes on for solo but produces no volume boost).
The channel switch still works fine. Any ideas why the solo button stops working when the amp warms up? Thanks

shytfayse · May 15, 2011

There is a PNP transistor, zener diode, a JFET, and the footswitch jack itself in the solo switching network. It may be one of these has a thermal problem where it turns on with heat. I would still check the footswitch and cable before tearing apart the amp as this is still the most likely problem. When the problem occurs, get a stereo/TRS 1/4" cord into the footswitch jack and short the ring to the sleeve with a jumper. If the solo control works, the problem is in the footswitch. If it doesn't, then the amp will have to be repaired. Hope you get it solved as the intermittent ones are the hardest to find and fix. - Pat.

myoung2746 · May 16, 2011

thanks i will try that

myoung2746 · Jul 13, 2011

I shorted the ring to the sleeve of the footswitch jack on the back of the amp and the solo will work. So I thought the problem was in the footswitch/cord.

I replaced the MIDI cord but that did not solve the problem.

The next step is to replace the footswitch I guess but I just can't imagine that the amp warming up would cause the solo button to malfunction if the problem was in the footswitch since the footswitch is no where near the amp's heat. Its obviously a heat problem because the longer I play the longer it takes for the solo function to kick in after I press the solo button, and then eventually there is no solo function at all unless I short the ring to the sleave on the footswitch jack on the back of the amp.

My gut tells me this is an amp problem near where the footswitch MIDI cord plugs into the amp, as this plug-in is further down the circuit board than the 1/4" jack i used to short it, leaving the possibilityt he MIDI plug-in area on the back of the amp could be faulty while still allowing the 1/4" jack to work when I short it.

Does this sound logical? Or am I off track . . . . thanks!

shytfayse · Jul 13, 2011

Like a moron, I did not ask if you had ver1. or ver2., and, I'm guessing you have ver2. Because the 1/4" ext switch works then most of the circuitry is working in the amp. I would still lean towards the footswich. I've seen the buttons go bad too many times. If it is thermal, then all you can do is open the amp, trace the circuit and reflow solder joints. I have a schematic for ver1 but not ver2. Maybe some else on here has one. If you're not up for that, and I don't blame you 'cause Mesa's are difficult to work on, send it to an authorized repair shop. - Pat.

myoung2746 · Jul 14, 2011

yes it is a version 2 rectoverb, i will prolly just try replacing the footswitch as soon as I find one with a return policy in case that doesnt fix it, thanks for the advice

myoung2746 · Jul 31, 2011

i had the amp fixed at a music repair shop and for anybody's future reference the problem was a 2n-6426 transistor on the main amp board that had to be replaced, thanks