2. amps-preamps
  3. 1132847783

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

Showing 7 responses by jond

jond's avatar
jond OP
5,694 posts
 
Well guys I looked at the fuse and it looks fine. I don't know how to test it. I'm afraid that Ecclectique is right and a bad tube took down some resistors or something like that. I guess tomorrow I'll take it over to Deja Vu Audio and see if Vu's tech can take a look at it. What a bummer! Anyway thanks for the responses everyone, I'll let you know how it turns out.
Cheers,
jond's avatar
jond OP
5,694 posts
 
Unclejeff,
I switched them both back one at a time and now I can't get any sound at all. The really wierd thing is all of the tubes light up and appear fine. I really can't figure this one out.
Thanks,
jond's avatar
jond OP
5,694 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?
jond's avatar
jond OP
5,694 posts
 
Guys,
Member Scifi walked me through testing my fuse with a voltmeter and the fuse is fine. It looks like it's either tube related or worse. I should be able to get my hands on a replacement quad of tubes today and if those don't work it's time for repairs. Wish me luck!
jond's avatar
jond OP
5,694 posts
 
Jea48,
The repair shop is where the replacement tubes are. I'll do whatever they tell me with the amp, it's in their hands. Thanks for your advice and for posting a link to a pic of my amp, it's a sleek little beastie don't you think?
jond's avatar
jond OP
5,694 posts
 
Well everyone, it turned out that all 4 tubes were bad and they took out resistors and caps. So Deja Vu has fixed the amp, I'll be picking it up on Friday and it only is going to cost $180.00. Woo-hoo!
jond's avatar
jond OP
5,694 posts
 
Jim,
I know what you mean! Slight change though, it was $212, still a great deal, but they're still waiting for a new fuse that they had to order over the web, so I won't get the amp until next week sometime. Nonethless I'm excited, especially since the new tubes I picked up were cryoed Valve Art GEC replica KT88's with virtually no hours. Since I've never had an amp that could run KT88's I'm really jazzed to hear them. When I do I'll report back.
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