THD Bivalve problem!!! Can anyone help?

[fishingboy]

Hi folks. Before I bring this amp in to a tech, maybe someone can give me some insight. Here is what happened:
I was playing a show last night with the Bivalve into a 1x12 4ohm cab. Sounding good then no sound. One 6L6 tube blew and has a grey cloud at the top of the glass, and both preamp tubes blew. NO FUSES seem to have blown. I replaced 3 tubes and all lit up, yet NO SOUND. Maybe someone can advise.....thanks.
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[Jazz P Bass]

There is a lot more to troubleshooting a tube amp than "they lit up"
About the only thing that can be surmised from that is that the heater supply "works".
Take it in to a tech.

[fishingboy]

Thanks for your post, but I found the answer. I tested all the fuses, as someone suggested, on a multi meter, and found 1 bad one. Amp is now working.

[hasserl]

But you still need to know what caused the failure. Just replacing the fuse doesn't fix the problem. Something caused 3 tubes to fail together, better figure that out, or take it to someone that can.

[fishingboy]

Can't a defective tube cause that problem??
Thanks man.

[Mick Bailey]

Can you post a pic of the grey cloud you describe? sounds like the vacuum may have gone on that tube. Any silver left?

[Jazz P Bass]

Can't a defective tube cause that problem??
Thanks man.

Yup.

[fishingboy]

Can't post a pic, but yes, all the silver is gone.

[hasserl]

Can't a defective tube cause that problem??
Thanks man.

A defective tube can cause the fuse to open, but a defective power tube is unlikely to take out the preamp tubes, and vice versa.

[trevorus]

Can't post a pic, but yes, all the silver is gone.

That usually means the glass envelope is cracked and leaked, which means the tube is shot.

[fishingboy]

Also, the bass player said he saw "sparks" just before it blew. One power tube and both preamp tubes blew, and the High Voltage fuse blew.

[Enzo]

If it works, stop fixing it.


I thought a Bivalve was a clam.

[portugaljazz]

try to see this link fishingboy ... I hope you can get idea to fix it by yourself

THD BiValve-30 Manuals, Support and Troubleshooting - Amps

[acorkos]

Also, the bass player said he saw "sparks" just before it blew. One power tube and both preamp tubes blew, and the High Voltage fuse blew.

did he see sparks before or after he spilled beer on your amp?

[hasserl]

Also, the bass player said he saw "sparks" just before it blew. One power tube and both preamp tubes blew, and the High Voltage fuse blew.

Not usually a result of a tube loosing it's vacuum. Something caused 3 tubes to fail, or blow, as you put it. 1 power tube and 2 preamp tubes. That doesn't just happen.

Enzo said stop fixing it.

I say make sure you take a backup amp with you.