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
Jond, if I understand you correctly you are going to take the amp and old tubes with you to the repair shop. They will be able to test the old tubes while you are there. Does the Amp have auto output tube bias adjustment for the power tubes, or do you set the bias mVDC voltage manually for the amp? If the bias mVDC voltage is way off you could damage any new tubes you would install in the the Amp. I still believe something is damaged in the Amp due to a shorted 6550 power tube...
fuses are usually checked for continuity with simple $3 continuity tester. in glass fuses you can see the broken thread of wire(sometimes).
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, sounds great. $180.00 thats not bad... Thanks for letting us know what the problem ended up being. I wish more members would follow through on their threads like you did.

Jim
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.