5:25 has crackling noise

Anyone experience this? Makes crackling type noise all on its own, all channels, all modes, guitar plugged in or not, foot switch plugged in or not. Tried different speaker cab - nope, this is the combo, by the way. Turning each and every knob makes no difference (though this SOUNDS like a dirty pot'). It did seem to have an effect when I plugged a 1/4 jack into each of the speaker outputs. Coating with DeOxit didn't seem to make much difference. The noise is barely audible when playing but will drive a person crazy when not.

Tubes most likely. Try tapping each tube with a pencil and see if that does it. If it does replace the bad tube(s).

Tapped on all of them, none appear to be microphonic or have an effect on the noise. I played again last night and the amp was quiet (no crackling noise) for about two hours, then it started crackling again. Based on a lot of search results, it leads to some sort of tube failure (power or pre); so I guess I will have start substituting some in.

Is it a crackling or more like a hum? Mine has started making this low hum. Initially I thought it was only on 5 watt mode but now I think I hear it on all modes. I swapped out a few tubes but that didn't seem to affect it. For you I agree, swap out some tubes anyway. Can't hurt.

It is definitely a crackling type noise, very much like a bad or dirty potentiometer makes, but is not (as far as I can tell), a bad pot'

Thanks for the response, by the way.

It sounds like a preamp tube. Tapping them is not a troubleshooting method for anything more than a microphonic tube. To trouble shoot the preamp tubes, take a new/known good 12AX7 and swap it into each preamp position, one position at a time. Test the amp in-between each swap to pin-point the tube that is potentially causing the issue. Thanks!

Thank you, I did In fact, just roll in a preamp tube into V1. It is quiet for the time being, but I will not be able to play it for an extended time this evening. I will try over the weekend and post the results.

This morning I played the amp for a short period and the crackling returned. Luckily, I still had the chassis removed from the cab from the other night; as with it out and everything more visible - I had a power tube red plating! I shut things down, let it cool off, and installed a new pair of power tubes. I have played it for about two and a half hours so far, with no noise. Hopefully, that is it. Thank you again for the help.

If the noise comes back, look at the screen grid resistors. They can be damaged by a bad power tube and will make crackling noises. R105 & R106. They should be 470 ohm.

Thank you, I'll keep that in mind...