Problem with one channel going out.....

OK gurus...I am at a loss and hoping someone out there can help.

I have had a problem with the "right" side of my system going out once in a while.  It has seriously impeded my ability to listen, as I am always anticipating the problem happening.  I have run through a number of troubleshooting steps, arriving at the conclusion that the problem is somewhere in my Manley Chinook.

Here's the basic specs on my equipment:

VPI HW-19 turntable

Graham Engineering series 2.2 Tonearm

Benz LP MC cart

Manley Chinook phono stage

Manley Neo-Classic 300B Preamp

Rogue Audio M-180 monoblocks

 

Some background on the issue: I have been plagued with one channel going out (meaning one speaker simply does not produce sound anymore....you can hear a hiss and sometimes a dramatically reduced, faint music)...but in essence, it's the right side going "out". This has been happening sporadically for years. I was certain that the problem was with one of my monoblocks which have been returned for service to Rogue twice (no definitive issues, just replace some historically problematic components) but the problem has persisted.

I even replaced one of the tube sockets because I got it in my head that one of the pins was loosely contacting.  That seemed to solve the problem.  Yay!  Well, I got one trouble-free listening session out of that "solution".

So, I continued listening, resorting to giving the amp a "whack" on the side when the problem arose.  You can imagine the fear and loathing associated with constantly waiting for the demons of analog to strike.

The other night I set out to burn a few CDs from my vinyl collection to listen to in the car.  The CD recorder has a meter showing the levels from each channel as the record plays...sure enough, the right channel went out during recording, and I noticed the right channel on the meter was also not registering anything.

This was a huge clue that the problem is NOT with the amplifiers, as the CD recorder gets its signal directly out of the preamp.

At that point, I tried everything I could think of to isolate the source of the issue, starting with swapping cables from one channel to the next and seeing if the problem jumped to the opposite side.

Sometimes I would swap input end of the cables only, then output end only, and finally swap the cables to the opposite channel altogether (to see if the problem is with the cable itself).  All of my testing points to the problem being somewhere from the Phono stage up to the turntable. (I even swapped each pair of tubes to opposite channels two at a time on the preamp).  Additionally, the problem only occurs with the preamp set to input 1, the phono input...but I lean towards the preamp input not being the issue, but rather the signal going into it.

Next, I swapped the tonearm cable inputs to the phono stage; the problem remained on the right side, so in my mind this rules out an issue with anything before that cable...perhaps my logic is off(?)

So, I focused on the phono stage itself. I opened it up and replaced all four tubes with the original ones supplied with the device when I purchased it.  They are perfectly matched, awesome tubes, I just swapped them out for some other crazy tubes soon after purchasing the unit.  No explanation, but you get it. A perfunctory visual examination of the interior components and soldered connections yielded no further clues.

Was pretty thrilled with the "new sound" and was perfect for the duration of my quick test, but when I settled down to listen to a record side, the right channel went out again.

So, I am now at a complete loss. I can't think of anything else aside from packaging the Chinook up and sending it back to Manley.  Before I do, I am hoping someone  out there may have some insight, or can poke a hole in my methods somewhere to help me figure out the source of this nagging issue once and for all.

Thanks!