'Whirring' / 'Buzzing' sound - but cannot diagnose fault
I recently picked up a pre-owned PS2 that make a 'buzzing' or rapid 'switching' noise whilst in-game. I have completely disassembled, cleaned and oiled the respective parts which needed it - still the noise continues. I have tried playing games with the top lid off and it is NOT the Disc Drive making the noise. I have replaced the Power Board - still the noise continues. The weirdest part is, during in-game menus and whilst a game is paused, the noise immediately stops, then resumes once the game is started again. It seems to be only when actual gameplay elements are being 'rendered' (if that's the correct way to put it) that the noise happens. I have tried 3 separate PS2 games and each yields the same result. I've tried the games on a separate PS2 and it does not make the noise. The model is SCPH-30003 R. Please can anyone suggest what could be causing this? I've searched google and youtube with every possible combo of relevant search terms I can think of but everything seems to come back to the Disc Drive, which I know is not the cause of the issue.