PS2 PS2 90004 modchip no image, seldom works normally

[Ps2enjoyerrrr]

Hey guys, got myself recently slim 90004, as I've discovered after buying lol it was modchipped with Modbo4, 3v wire was cut and isolated so someone has tried to turn it off?

Anyway the issue is that I'm getting no image nor sound on boot, fan starts spinning for 2-3 seconds then stops. Sometimes when I'm rebooting many times with START pressed on gamepad, or just randomly, I'm getting an image and everything works normally, even played for 1+ hour, no issues. But then it stops booting normally again and there's no image on screen.

Is it chip causing the issues, or what can it be? When it works, it works: both mc slots, gamepads, usb, gaming, everything works and boots in general so at least it's not dead? I also heard dead cmos might be causing issues esp with modchips, can it be the culprit? I have literally no knowledge about microelectronics so I can't really tell if soldering is good/bad/shorting or what else, capacitors are looking normal so far, not leaking, not blown etc.

 

[Ps2enjoyerrrr]

Somehow replacing cmos battery and putting it in the right way (it was just under the heatsink, not inserted propertly into the holder & under these metal pins on the right), helped so far, console boots normally every single time, "sees" MCs, gamepads, plays games etc. I'm gonna test it more of course. I also cut ground wire and isolated it maybe that helped too.