Chasing down the problem


Couple of nights ago, I was listening to my mono block tube amps and after about ten minutes the right channel goes silent! What the heck!! So begins the search for the culprit...is it upstream of the amps, or is it the right side mono block that has an issue...and what kind of issue.
Luckily, I own another stereo ss amp, so the first thing to do was to hook that up and see if the problem continued. This would eliminate a few pieces of gear as the culprit...basically everything in front of the tube mono blocks...except the connection from the preamp to the mono blocks...the ic’s.
The system played fine with the stereo ss amp in the chain...therefore leading me to believe that the following components were not at fault...1) the front end digital player and the front end turntable set up ( I did play both to be certain) 2) the tube preamp, 3) the connections between these components...speaker cable and ic’s ( I use different ic’s and sc’s to connect the preamp to the ss amp than with the tube amps).
The next day, I hooked up the tube mono blocks again...and this time after making sure that the connections at the amps were tight and that the tubes were all re-seated. Music played again in both channels ---for about twenty minutes! Then the same issue reared its head again, the right channel was silent. Hmm.

Therefore, unless I am wrong, the only two possibilities left are the right tube mono block...or the right ic feeding that mono block from the preamp. My next thing to do was to change the ic’s for another pair ( could have swapped left for right, but since I have other pairs of ic’s that i know are good, i figured why not try this next) Plan being to check the ic’s and then finally start to move tubes from one mono block to the other and vice versa to see if the issue changed channel.
Last night I listened to the same set up but with just the ic’s changed out between the amps and the preamp....and no problem. ( this after a two hour session).
Hopefully, I have identified the issue..would seem that the original right side ic has a iffy connection somewhere ( a lot easier to address than to have to get the mono amp worked on).
Anyone else have a problem like this that took a little ’work’ to identify?

128x128daveyf
@gdnrbob  I could do that, but i am hesitant to do so as the amps are "theoretically' under warranty. I say "theoretically" as you never know with this stuff until you request service!
So tonight I swapped out the 12ax7 driver tube...and after a few minutes of idle power...a loud and nasty hum and buzz through my right speaker! ( the same channel that was acting up before!) I quickly powered down...and decided to change out all of the power tubes. ( I figured this might be a classic power tube failure). Upon replacement of all KT150's, I powered up again. This time, no loud hum and buzzz...no apparent issue at idle. I switched on the high voltage...and sure enough..same channel is still down!..:0(  
I'm pretty flummoxed at this point, so I think next is off to the dealer.

Here's why tubes can be a major PITA! 

Tonight, I figured one of my tube mono blocks was down...so I swapped in my ss Rowland stereo amp ( in place of the tube mono blocks) for a night of music and lo and behold...the same darn issue persists!! No sound out of the right channel! 
This is so very odd as my first thought, see my OP, was to do this test and the sound was fine before when the ss amp was in the chain. This would seemingly now mean one of two things..a) the preamp has a problem or b) the right speaker is blown. 
I swapped over speakers...put the left speaker on the right side and vice versa ( easy to do with stand mounts, luckily) Nope--the right channel is still silent. Hmmm. Seems to be a preamp issue ( which could still mean a tube has gone away, as I use a CAT tube preamp...) 
So, onwards we go...
@jetter looks like you you’re right in regards to the preamp... although I am so surprised that all was fine when I hooked up the ss amp and played it for a few hours previously. Any idea how a preamp tube can cause one to lose sound in one channel?