Diagnostic - Pathos Logos amp

[DimiSakis]

Hi everyone!

I am writing to better understand an issue that my amp displayed today.
Specifically, the amp gives a periodic popping sound on the right speaker, even at 0 volume. The amp is question is a Pathos Logos that I recently bought used (worked fine until today!).
Something to note is that even if I remove the right channel tube from the pre-amp stage, the popping sound continues - so it shouldn't be a problem with the tubes or the preamp, right? Other things I tried were disconnecting all sources, changing power cables, and swapping the speakers, nothing made a change (other than the speaker swap, which moved the issue to the other channel )

Does anyone have an idea as to what may be causing this? Is it more likely to be an issue with the power supply or the power amp? My main fear is that the problem could be with one of the huge capacitors in the power supply, which would cost quite a bit to repair..

I am attaching the service manual in case useful for anyone who can help on this
I uploaded a video that displays the problem in this link:

https://imgur.com/a/oeNse9V

Thanks!

 

[Ray Gianelli]

Hi everyone!

I am writing to better understand an issue that my amp displayed today.
Specifically, the amp gives a periodic popping sound on the right speaker, even at 0 volume. The amp is question is a Pathos Logos that I recently bought used (worked fine until today!).
Something to note is that even if I remove the right channel tube from the pre-amp stage, the popping sound continues - so it shouldn't be a problem with the tubes or the preamp, right? Other things I tried were disconnecting all sources, changing power cables, and swapping the speakers, nothing made a change (other than the speaker swap, which moved the issue to the other channel )

Does anyone have an idea as to what may be causing this? Is it more likely to be an issue with the power supply or the power amp? My main fear is that the problem could be with one of the huge capacitors in the power supply, which would cost quite a bit to repair..

I am attaching the service manual in case useful for anyone who can help on this
I uploaded a video that displays the problem in this link:

https://imgur.com/a/oeNse9V

Thanks!

I would doubt a filter capacitor issue, given that the amp doesn't look that old. I would suspect the phase inverter tube or one of the output tubes.

 

[DimiSakis]

I would doubt a filter capacitor issue, given that the amp doesn't look that old. I would suspect the phase inverter tube or one of the output tubes.

Thanks for the input!
The only tubes the amp uses are in the preamp stage, and those work fine... (inverting them or even removing them doesn't stop the popping sounds on the right channel)