Maybe, just check the PSU? Especially the electronics that provide 12v for the console.
Originally Posted by ShadowFXD
I'm no hardware expert, but I think that I remember that the PS2's 12v line is used exclusively only for the DEV9 interface (Which is what your NA gets plugged into).
The first generation PS2s had 8.5v PSUs, and I remember something about a change to 12v PSUs to support the HDD unit directly.
SCPH-10000 S. MINOKAMO v1.01 (Defunct)
SCPH-10000 S. KISARAZU v1.00 (faulty)
SCPH-15000 S. KOHDA (With warranty seal!) :D
DESR-5100 S. EMCS