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THD Bivalve problem!!! Can anyone help?

fishingboy

Gold Supporting Member
Messages
106
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.
 

michael.e

Silver Supporting Member
Messages
20,505
I would run it hard for a while to see if you can replicate the blowing. Perhaps something is making it blow.
 

Stu Blue

Member
Messages
3,166
I would run it hard for a while to see if you can replicate the blowing. Perhaps something is making it blow.
A power valve shorting out can and often does damage other things... all too common with current production stuff. That's why it's worth paying extra to buy from from a dealer who seriously tests his stock. The boards on THD amps are built to NASA standards... real rocket science.
 
Messages
6,858
A power valve shorting out can and often does damage other things... all too common with current production stuff. That's why it's worth paying extra to buy from from a dealer who seriously tests his stock. The boards on THD amps are built to NASA standards... real rocket science.
:agree Inside and out....few amps or anything else is built this way.
Check out the new forum ...
http://fothda.yuku.com/directory#.Tx5X-aVSSHh
 

SinkingShip

Member
Messages
190
I did the exact same thing several years ago, blew both preamps and one power tube and 2 of the fuses. No logical cause until a long time later I realised how easy it was to bump the ohm switch to a not ideally matched position, perhaps not ideal especially when on high volts setting and really pushing everything very hard, on that occasion I blew another 2 fuses before I swapped the ohms back to better match. Never had a problem since after at least 4 years now using numerous valve types and brands, but I rarely run at high voltage which perhaps also helps reduce blowups I'm guessing.

Every time I play now I reach behind and just check I havent bumped the switch on back while loading in. I know you can run the ohms at any setting and not really harm the amp itself.....but some valves(brands or type) possibly do not seem to like everything at full tilt and ohms not matched at same time ??
 




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