SC20 weird noises

Sound City SC20 & SC30
1

I wrote to Sound City support via email and they recommended I post here.

My SC20 combo is making some weird noises. Randomly, it will start popping and clicking and sometimes whistling. It’s totally inconsistent but when it happens, it persists for a long time. Some days, it doesn’t happen at all and some days it happens constantly. It happens with or without anything plugged into the amp. It seems to be present on both channels and in the reverb signal. I haven’t taken the amp out of the house and it’s always on the same power supply. I wonder if you have any ideas about the cause or solution?

If it helps, I took a video and uploaded it here:

2

It’s definitely haunted… Thanks for coming to the forum. Bye.

Welcome oldangelmignight!

This sounds like a preamp tube going bad (maybe heater-to-cathode leakage) and possibly microphonic. Can you remove the metal cases and tap on them with a pencil to confirm better? It did sound like the noise and clicks became synchronized with your tapping on one or a few of those tubes.

Also, this is a really good example of a well-posed question. Thanks for going to the trouble of uploading a video.

@Gil any other reasons for clicks and pops from your experience?