2. amps-preamps
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Help troubleshooting amp

Hi,
When I turned the system on this morning in anticipation of a long holdiay of music there was no signal in my right channel. I first checked all connections which were fine and then I subbed in a pair of replacement tubes for the right side of my preamp, still only on channel. I then switched my attention to my amp, I switched both pairs of 6550's from left to right. Now no signal in either channel! This leads me to beleive that the trouble rests with the amp. I'm going to try switching 6550's back again but one at a time to see if I at least get the left channel back. Regardless I'm pretty sure it's a tube issue but if anyone else has any ideas I'm listening. Why do these things only happen on weekends and holidays?
128x128jond
marakanetz's avatar
marakanetz
5,473 posts
 
Ecclectique might be right.
usually the faulted resistor looks bad and acts either as an open ckt(very similar to a fuse i.e. as a part of ckt protection).
kgturner's avatar
kgturner
664 posts
 
ah, the many joys of tube amp ownership. almost makes me want to go back to solid state. almost.
musicslug
430 posts
 
you haven't told us what type of amps you have but...
on my Cary SLAM-100's there are TWO fuses per monoblock - one's just for the tubes and I forget what the other's for - and I have had situations where one of them blew and there was no sound but the tubes still lit up fine.
jond's avatar
jond OP
5,911 posts
 
Sorry my amp is a Graaf GM 5050 pushpull stereo amp using either 6550's or KT88's. It currently is tubed with EH6550's. I thought that you could tell if a fuse was blown by just looking at it, am I wrong?
musicslug
430 posts
 
sometimes, if the break in the fuse is tiny, you need a magnifying glass to see it. assuming you have spare fuses on hand, simply changing them will be a diagnostic if you're stumped. as I said, my monoblocks have two fuses per side, and one of the fuses can be blown (resulting in no sound) while the tubes still light up.
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