Einstein 100w blow up both power tubes, help please!

  • Thread starter Thread starter gramaser
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gramaser

gramaser

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Hi guys,

My 100w einstein head, last week blow up the outer tubes fuse.

Took it home, and replaced the fuse with one of the same rating, changed the outer tubes with matched fresh ones (I always buy tubes in octet matched sets), checked the bias and the outer ones were way off (110ma for el34's) while the inner ones were 64ma for el34's.

Adjusted the bias for both the outer and the inner set, played it for one hour, checked bias again, bias ok, amp played ok.

Yesterday at one our into the rehearsal, suddenly the amp blows both fuses, inner and outer, and completely shut down, now won´t even turn on and I can´t even remove the outer tubes fuse holder.

I suspect this can be related somewhat with the bias circuit, but I'm not really sure about what's going on with the amp.

As I don´t have a amp tech near me, can anyone please help me on this?

Thanks.
 
All the "good guys" are pretty much busy these days because of the Namm. Please be a little bit patient. Probably you have to send an email directly to Peter.
Good luck
 
Thanks for the tip!

I guess I will email Peter, and see if he can help me.
 
It's difficult to say with any confidence what the issue is here, but you have to start small and look at the possibility of additional tube failure.
If the fuse is difficult to remove, the ends could be fused (no pun intended) to the holder contacts after a high current spike. Every once in a while this happens, and if you cant remove the fuse holder cap, then it becomes necessary to replace the entire fuse holder.

Generally it's best to replace all the tubes when you have a tube failure. It's possible the outer pair blowing the first time stressed the inner pair to the point they were weakened and ready to go out, and when one of them did, it pulled a tremendous amount of current and tripped all the fuses. Your new outer pair may be okay, but then again may not be. You should really replace all 4 tubes this time if you can get the fuses replaced.
 
Ive had the fuse break making it a pain to get the holder out
 
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