Mesa Boogie DC-3 Clean Channel Not Working

[jimsz]

I've been trying to troubleshoot the Clean channel of my 1993 DC-3. I tested the gain pot, which was making some noise before the trouble started. As well, it would literally cut out altogether if dimed over. Testing it on a multimeter, it appears to be functioning fine, but I still don't get any signal to output. The Distortion channel gain pot was also making some noise, but a blast of De-Oxit fixed that easily.

This problem started out as an intermittent problem of noise, then an intermittent problem of suddenly having low volume on the channel, eventually fixing itself over a bit of time. Now though, that channel doesn't work at all.

Sorry about the "SuperReverb Amp #41" label of the pic, it got mixed in with other pics.

[selloutrr]

just curious you have tried the ch3 preamp tube? and cleaned the sockets. I'm assuming the rest of the amp works.

have you tried probing through the circuit with a signal tracer?

[jimsz]

just curious you have tried the ch3 preamp tube? and cleaned the sockets. I'm assuming the rest of the amp works.

I've tried the tubes, swapped them for known good ones. I haven't cleaned the sockets yet. Will do that. Yes, the rest of the amp works fine, the distortion channel is awesome.

have you tried probing through the circuit with a signal tracer?

Unfortunately, I don't have one of those, just a multimeter and oscilloscope.

[selloutrr]

you can build one pretty easily if you have an extra amp to use as the speaker. hoffman amps has a DIY.

http://www.el34world.com/Hoffman/tools.htm

[jimsz]

you can build one pretty easily if you have an extra amp to use as the speaker. hoffman amps has a DIY.

http://www.el34world.com/Hoffman/tools.htm

Hey, that's great. Don't have any extra amp, but I can probably source out a cheap one somewhere. Thanks!

[selloutrr]

have you tried chop sticking the amp while its on and seeing if you can force a component to move / short and pass signal?

[jimsz]

have you tried chop sticking the amp while its on and seeing if you can force a component to move / short and pass signal?

Yes, I have, all over the place. I get some loud harmonics coming through in the same area where the gain pot from the clean channel connects to V4. Other than that, nothing there or anywhere else seems to make any difference if moved around.

That's what makes this odd in the fact that even at that connection point, I still get some output.

[selloutrr]

have you tested the switching function?
resolderthe point you can make pop when chop sticking.

[jimsz]

have you tested the switching function?

No, that would be another one to do. Interestingly, this amp didn't come with a footswitch and I wound up buying a third party one; Apex.

resolderthe point you can make pop when chop sticking.

Will do. Thanks.

[jimsz]

All fixed, working better than ever. Looks like it was some cold solder joints on V1 and possibly problems with the socket on v4. There was a bit of hum but now it's dead quiet with both channels working great.

Thanks for all the help guys, much appreciated.

[selloutrr]