Mesa Heartbreaker- Tech question, please

[BStringThumper]

Hi everyone. I have a Mesa Heartbreaker that has very low volume. All tubes have been tested, sockets retightened. I'm running 6L6 tubes, I set the bias to spec.. All voltages are within spec. Power section appears OK. I had the amp turned on doing signal tracing. Channel one was amplified through v1 & v2. Now for the strange part. I touched the signal trace probe to v7 pin 1 and there was a pop through the speaker and the amp started working. Full power, switching, both channels. I turned the amp off and then back on, same problem, very low volume again. I touched v7 pin 1 again, it pops through the speaker, then the amp works again. After my last capacitor lesson from the help from Jazz P Bass I'm leaning towards a capacitor acting up. This amp is 11 years old, slight 60hz a/c hum, it would probably be best to recap it anyways. I'd appreciate anybody's thoughts. Thank you.

[kg]

i don't have a schematic handy nor do i know the layout by heart... what node is v7 pin 1?

[BStringThumper]

Hi KG. Thanks for your reply. The node is the 12AX7 tube circuit for the effects loop (return/send). I resoldered the pins on all the 12AX7 sockets. I cleaned all the input and output jacks. I wonder if I should have started there. Now the amp IS WORKING. YAY! Not sure what the fix was but I'll be watching it carefully. Thanks again.

[Enzo]

Very likely the solder on pin 1 was cracked, and youching the probe to it made contact and teh spark kept the circuit goping until you turned it off. REsoldering would corrct that, as you found.

[BStringThumper]

Enzo, it's so good to see you back! I hope all is well with you.

I'm happy this amp is working now. I'm learning something new everyday. I appreciate the help you've given me. I've learned a lot reading the expert advice you've been so kind to give to others, too.

Welcome back!

[km6xz]

You will probably see this symptom again, in other amps. A common cause, very common, is oxidized normalizing contacts on the effect send/return jacks. A jolt of signal, can if the layer thickness of the insulating layer is thin enough, be broken through so current can flow again. Sitting for a while and the oxide builds recovers and acts like an insulator again. Use a de-oxidizing chemical to remove the oxide which leaves a thin oxygen barrier to prevent it from building up for a long time.
Any intermittent level or intermittent distortion that responds to signal level, worse at low levels, should make a tech suspect the send return jack normalizing contacts. The easiest check for it is simply inserting a jumper cable between the jacks. If that is the problem the signal level and fidelity should return to normal. If not, then go on to normal trouble shooting and signal tracing.

[BStringThumper]

Hi Km6xz, thank you for your advice, that was very informative. I think I had both the oxidation and broken solder joint happening on this amp. For now on after initial amp inspection I will clean those jacks and resolder those pins. I'll pick up some deoxit (sp?) asap. Thanks.