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How do i tell if i have a failed tube in my preamp?

Today after firing up system I noticed a distortion from all three drivers on one channel. Next I went from turn table to cd.Same thing,so I tried moving /wiggling all cables. No help or any change whatsoever.Could this be a tube going out in my BAT pre? Can I get an answer without a tear down please.I have extra tubes .6922s I believe.Thanks,R.W.
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lostbears's avatar
lostbears
538 posts
 


Are all the tubes lit up?  Take the tubes from one channel and but them in the other. Does the distortion move to the other channel? If so it is a tube that has gone bad. Then just go one by one until you find the tube. Be sure you unplug the preamp when you swap tubes.
rickw062's avatar
rickw062 OP
23 posts
 
Just changed cables from left to right on pre.Problem still in same channel.Now i have isolated it to left mono block amp. I guess I'll open it up and check the caps and grounds before sending out for sevice.It has had a slight hum for awhile but did not draw attention while playing.Hmm.R.W.
yogiboy's avatar
yogiboy
5,655 posts
 
Just to make sure try swapping the speakers.
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