Jcm2000 - hum

[lowell]

I've had a few of these amps in the past week or so and they have all hummed from the SAME PROBLEM. There is a treble bleed cap across the power tube plate/screen closest to the end of chassis. This cap fails and takes the screen resistor with it. In each amp I've fixed the screen resistor is visibly cracked lengthwise. Just thought I'd share to save someone else troubleshooting time.... check this first! Replace that cap w/ higher voltage rating silver mica and replace the resistor.

[Enzo]

Yes, the dreaded C46. It's not there for tone, it is there for stability.

[lowell]

ah... yes for high frequency oscillations?