Mesa/Boogie Maverick repair nightmare

[Enzo]

If you lack a scope and signal generator, you can still follow the signal. Just apply ANY fairly stable signal to the amp. I often use music from my bench stereo. And instead of a scope you can use the AC scale of your volt meter. The voltage levels of signal through a tube amp are usually easy to detect with a meter. A "signal tracer" is a handy tool in any audio shop. it is essentially a small amplifier with a probe for an input. SO while a scope is visual, the tracer is aural, but either one lets you hear/see the signal in a circuit.

[Chuck H]

If you lack a scope and signal generator, you can still follow the signal. Just apply ANY fairly stable signal to the amp. I often use music from my bench stereo. And instead of a scope you can use the AC scale of your volt meter. The voltage levels of signal through a tube amp are usually easy to detect with a meter. A "signal tracer" is a handy tool in any audio shop. it is essentially a small amplifier with a probe for an input. SO while a scope is visual, the tracer is aural, but either one lets you hear/see the signal in a circuit.

Agree... But I want to add that for this to give any useful troubleshooting info it's essential that the tech has a good understanding of the circuits so they'll know what to expect. Short of that, a signal generator (any signal, as Enzo pointed out) and a scope are the better tools so that amplitude can be witnessed.

[evil79]

Just an update: thank you all for all the help. I keep getting called into one of my 3 jobs and haven't had a solid chance to test everything y'all have suggested. I did have a chance today and one out of the quad of brand new JJ EL84's cracked on me while the amp was on. I'm so frustrated. Goddammit! So let me deal with this and I promise I will keep everyone informed on what is happening with this amp. Massive respect to everyone who has chimed in.

[Chuck H]

Hmm... I've never had a tube spontaneously crack. I've head of them melting from running too hot. It's too bad we don't have a bead on the operating conditions yet. If the failure was indeed spontaneous under normal operating conditions you should be entitled to return the three remaining tubes for a replacement quad if they're still within the warranty. Of course, if you're like me you already had the tubes and didn't test them within warranty after purchase If the tube cracked because it was thermally stressed you may have a bias problem on top of the other issues. Related? Maybe. since you worked on the cathode bias circuit you should be prepared to check current the moment you have known good tubes in.

[evil79]

Hmm... I've never had a tube spontaneously crack. I've head of them melting from running too hot. It's too bad we don't have a bead on the operating conditions yet. If the failure was indeed spontaneous under normal operating conditions you should be entitled to return the three remaining tubes for a replacement quad if they're still within the warranty. Of course, if you're like me you already had the tubes and didn't test them within warranty after purchase If the tube cracked because it was thermally stressed you may have a bias problem on top of the other issues. Related? Maybe. since you worked on the cathode bias circuit you should be prepared to check current the moment you have known good tubes in.

I contacted the business that sold me the tubes. They are very reputable and I have been buying from them for years. But yes, it did occur to me that my amp could've been the cause and not the tube. We'll see what they say. I'm at the end of my rope with this amp. I've had a few of my amp tech buddies over to check it out and they are stumped as well. It's a massive headache. I do have a probe and a listening amp, and an oscilloscope, but have never been shown how to use an oscilloscope properly. Or at least how to interpret the information that it gives me.