I thought the ACPI wires on the P1900 were thin and plugged into a header.
What does the manual say about that location?
The problem is the manual is kind of unclear on this spot. It looks like this is where JP3 is (which is supposed to be the isolated ACPI relays) but it also says they're supposed to be green and black.
Not sure if this is related but the P1900 I got is v2.2. The only manuals I can find are for v2.0 and v2.1 - maybe something changed since the last version??