Crackling sounds on LSS Channel 1

Hello everyone. I'm new here. Would appreciate some help on my LSS. There are loud cracking sounds that only appears on Channel 1 of my LSS intermittently. These noises happens for up to 30 seconds, sometimes longer and then stops and after a couple of minutes come back on. Regardless of which power setting used. The problem does not happen on Channel 2. I tried switching to Channel 2 when the noise comes and it disappears but is still present when I switch back to Channel 1 after a while. I downloaded the LSS schematics and from the looks of it both channels share the preamp and power tubes so that kinda suggest that it's unlikely that one or more of the tubes are failing. In which case both channels should have the noise problem, no?
Has anyone here come across this problem and how did you sort it out?

Cheers,

Moderneagle

Thanks. I suspect the noise is caused by a component maybe a bad cap in the Ch1 board circuitry. I've changed the pre tubes out but that didn't help any. Will continue checking. If anyone has come across this please do share. Gracias.

Update: it was a bad cap in Ch1 tone/gain cct.

moderneagle said:

Update: it was a bad cap in Ch1 tone/gain cct.

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Get similar crackling sometimes on my LSC too. How did you find and fix the problem? Tech?