CCV Hum

[tims210]

I'm trying to troubleshoot a hum that recently appeared regarding the loop's operation. I recently bought a reverb/delay combo pedal to use which worked fine with the amp. I started noticing a hum develop after a while and thought maybe the pedal went bad. I was also using speaker cables to connect it which I've read can create noise. When I turned the loop off the hum disappeared. To further investigate, I removed both cables from the loop, jumped it with an instrument cable, and turned the loop back on. Now dead silent. I went and turned the loop off and the hum returned. It's like it's behaving in the inverse of when the pedal was plugged in. This is happening with both the jumper cable plugged in and also with it removed. Also happening on both channels. Tried a different guitar and cables too and no difference. Can anyone lend a hand on what might be going on here? I don't know what era my amp is. All I know is that it has the upside-down PCB.

Thanks in advance.

 

[Smash]

Is it a hum or a ground loop? Is it the mains? Does it go down when you turn down volume and up when you raise volume?

 

[tims210]

Not familiar with how to answer your first two questions, but yes, it increases with more volume.

 

[glpg80]

Tube buffered loop?

Could be a bad tube.