3 things I imagine you could have done to it:
1- Disconnected the flat cable from the main board.
2- Punctured the flatcable with a screw or plastic pin on the case by accident.
3- Broke the middle track (gnd) by bending it while manipulating the PS2 unit, by accident.
The 3 will lead you into a unit which gets power but doesn't lit the red light. A pico-fuse on the motherboard labeled "PS1" protects the standby circuit. It usually blows when the flat cable gets shorted by a puncture.
Good luck figuring this one out. Any doubts I am here to try helping
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)