intermittment volume drop in 5e3

[dubs]

Built a mojo 5e3 kit and it powers up and sounds fine. voltages seem fine. However every now and then there is massive volume drop in the normal channel (crank it to 10 and you can barely hear it). It lasts for awhile and then it goes back to normal. The bright channel works fine.
I tried looking for cold solder joints but looks ok.
Any thoughts?
thanks in advance.

[Bruce / Mission Amps]

Built a mojo 5e3 kit and it powers up and sounds fine. voltages seem fine. However every now and then there is massive volume drop in the normal channel (crank it to 10 and you can barely hear it). It lasts for awhile and then it goes back to normal. The bright channel works fine.
I tried looking for cold solder joints but looks ok.
Any thoughts?
thanks in advance.

Maybe a bad volume pot, bad triode in the first preamp tube, input jack is faulty shorting to ground.
If none of those, it still could be a bad solder joint though and usually is even though we look at them with critical eyes.