>>"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."<<
>>>>>>>>>>
Just a guess, a bad shorted 6550 tube. The bad tube may have damaged something in the right channel. Installing the bad tube in the left channel may have caused damage there as well.
Post a thread on Audio Asylum on their tube forum and ask your question.
http://www.audioasylum.com/audio/tubes/bbs.html
>>"This leads me to beleive that the trouble rests with the amp."<<
>>>>>>>>>>
Just a guess, a bad shorted 6550 tube. The bad tube may have damaged something in the right channel. Installing the bad tube in the left channel may have caused damage there as well.
Post a thread on Audio Asylum on their tube forum and ask your question.
http://www.audioasylum.com/audio/tubes/bbs.html