I just troubleshot and fixed my amp

[DGDGBD]

It was making intermittent crackling and popping noises. Its a spitfire clone that I built from scratch several years ago. I thought...crap! it could be a hundred different things, including my "not quite professional" build quality. Some of the jacks were coming loose so I tightened them up. No difference. Crackling would get louder with the volume pot, so I concentrated on the pre-volume circuit. I swapped out the preamp tubes, but no luck there. Then I remembered that a few months ago I swapped in an old mustard cap that I had laying around, to see if it would enhance the tone. It was the coupling cap from V1 plate to the volume pot. Swapped it back out with a new cap and problem solved. I guess the old mustard cap started to leak.

[sdgvintage]

one true sign of a leaking coupling cap is when you adjust the volume pot, if you hear crackling while you are turning the pot, the cap is leaking or the pot is dirty.
When you get DC on a pot it crackles when you turn it.
Some circuits like the tweed bassman leaks dc onto the presence pot by design.
I recently dealt with a crackling tweed amp that was suffering from tweed disease. That is when the tweed board causes the crackling

[RussB]

Very cool :)

Part of the fun of building them is figuring out the bugs

[David Robrecht]

From one "Dave R." to another, well done!
Dave

[donnyjaguar]

Nice work. IMO, troubleshooting new builds is harder than amps that have been in service because you are dealing with more unknowns.