Roland G-800 - Random (electrical) crackling noise from line out and headphone jack

[m-techn1k]

Hello.

I have a Roland G-800 that I bought in the late 90s. It's been working absolutely fine until a few months ago when it starts to crackle randomly. The noise would disappear with the volume turned down fully. But even at 20% volume and fed to the amp and speakers, the crackling sound is pretty loud. It's random though. Sometimes it doesn't happen for even half an hour, but other times it suddenly does this after only a few minutes. Sometimes, the sound (e.g. Piano) gets distorted too and the only remedy is to turn off the keyboard and turn back on.

I also tested to see if it's just coming out of the line out (to stereo amp and speakers) by checking if the crackling noise would also be heard when using headphones, and it does.

I've cleaned out the volume slider with contact cleaner and there is no static noise when changing volumes, which indicates the contacts are clean.

I can change instrument sounds with no problem, which makes me think that the XPGS Module/Card might be OK. All other functions work fine. MIDI also works fine and no crackling sound can be heard (I suppose because it's digital signal out to the computer, and the computer is what does the Digital-Analog conversion).

So that led me to believe that either the power supply (made by KARTIS) has a problem, or the Audio Board (ROLAND), or the CPU Board (ROLAND).

I'm wondering if anyone has come across anything like this, that would hopefully point me in the right direction as to which component needs to be checked/repaired/replaced?

Thank you in advance.