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Help me diagnose the problem

I've got a Rogue Tempest II Magnum. A couple weeks ago I heard a 'pop' and then noticed that the left channel wasn't quite right. Further probing led me to the KT90 in the V1 position- it was not hot to the touch. Mark at Rogue suggested I check the fuse to V1. Sure enough, fuse blew. Tip off was the tube could not be biased. Put in a new fuse, and we're good.

Today- I heard something not quite right from the left channel again. Popped the lid, saw I could not bias V1. Pulled the fuse and it was blown.

2nd V1 fuse blow in as many weeks.

Why am I blowing the V1 fuse? FWIW, the amp is nearly 4 years old. Could a tube issue be causing the V1 fuse to blow?

Thanks!
128x128zavato
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
It could be a tube issue, why don't you change out that KT90 for a new one. If the problem goes away, you know it was a bad tube, if the problem persists, then you have another problem altogether. One that would probably require professional service.
slikric3000
638 posts
 
I got the same crap, ain't the fuse though. Something more evil. Pops are tube like at least in my short experience, mine was two thumps. Anybody know what the thumps may have been ?? I got some cheap PCC88's from across the pond, a well known brand, I forget I would have to dig them out, pop and that was the end of the tube. It would still work but with static. A couple of those tubes popping and they came out.

I suspect my thumps were caused by moving my speakers a few inches, at least that is what I was doing when it happened.
newbee
4,751 posts
 
Seems to me that it is possible that when your first tube shorted out that it burned out a resistor in the bias circuit for that tube. A very common occurence in tube amps for this to happen. Some times the tube comes up when changed but the bias is not controlled and the second tube was overloaded. Ask Rouge if this is possible for your amp. If so find a techie to replace the resistor. It's not a big deal if you have a local shop. If not Rogue should be able to help.
zavato's avatar
zavato OP
1,391 posts
 
I am going to move the suspect KT90 to a different tube socket. If I continue to blow the V1 fuse it's not the tube. If I blow the fuse corresponding to wherebI move the tube, It's the tube-
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