I'm in trouble with this sound

[martin manning]

Paralleling a good cap over one that is failing by internally arcing would not eliminate the problem, but it might have some effect. Because pulling the PI tube stops the snapping, the reservoir, OT, power tubes, choke, and screen filter cap are eliminated. First I'd try plugging one end of a cable into the return jack to disconnect the signal from the preamp. Then I would try lifting one end of the 22k power supply dropping resistor to disconnect all of the filters downstream of the PI. If you get the same behavior then that would isolate the problem to the PI stage.

[pamaz67]

do yourself a favour and build a simple tool, by using a 100nF 630V capacitor. Solder a wire to one of the cap's lead, and stick it to ground of the amp. Get yourself something like a chopstick, and fix the capacitor at the chopstick with electrical tape . Do it so that the remaining lead of the cap could be used as a test lead.
Once you have such tool, you will be able to ground dynamically any point of the amplifier. So, by using it you will be able to find where the noise come up. Using the schematic, go back from the power amp input toward the preamp input, and you'll be able to understand where the problem lies. faster than an oscilloscope for finding such problems.

[talbany]

First couple of things I thought was 1. Cell Phone or Laptop nearby and 2 a bad filter cap (Discharging)
If you have a set of alligator clips you can clip in a new cap and just disconnect the Gnd side of your suspected bad cap. That way you don't have to pull the cap completely off the board to check it. If it's not a cap the next thing I would check would be cracked solder joint in the H.V section that's causing it to arc out, although, those generally tick at a faster rate.Generally


Good Luck!

Tony

[Guitarman18]

Hi Dariez,

I had a similar problem with one of my new build amps.

I went through everything to try to fix it and was almost ready to put it in the trash. However, 2 things were causing the issue. Apologies if they have been mentioned already.

1, Switchcraft switching jacks which had a bit of dirt in the contacts - particularly on the effects loop.

2, I discovered by accident. Some of my amps don't seem to suffer as much as others, but with this particular amp it seemed okay some days but others, it was terrible. The culprit was the mains LAN cable that we use in our house. When it is just idling, it just clicks, but if one of my kids is gaming, it sounds like a waterfall! Once unplugged the amp was perfectly quiet. It took me almost a year to figure that out (not constantly working on it obvs , but coming back to it every few months to see if I could make any progress).

This may not be the reason for your issues, but it might at least help to eliminate a possible cause.

Best of luck.

Cheers,

Paul.

[rootz]

Hi Paul,

I experience the same interference in my amps on certain moments. Sometimes when doing recordings. Never found a solution for this kind of interference or noise. Have you got any idea where the noise enters the amp? Via the guitar probably, but also over the mains maybe?