Spilled water into system; MOBO or PSU?

[ultrarunner100]

Hi;
My brother spilled water (plain ol' H2O) into his HP Pavillion Elite HPE the other day. The computer was running, and it shut down. He tried to restart, but nothing happens.
After allowing it to dry a few days, all that comes on is the green LED on the rear of the PSU (always lit when the PSU is turned on). Pressing the power button on the case does nothing.

After running through the troubleshooting sequence on the HP website, he ordered a new MOBO.
Now, after reading another thread here, I find that it could also be the PSU.
I am afraid to plug a new MOBO into the old PSU, since a bad PSU could fry the new MOBO.
Is there a way to test the PSU alone?

I have another PSU, from a non-HP system, but it is not compatible. The Antec supply I have does not have the 24-pin main power plug; it has only 20 pins, and the separate 4-pin plug for the CPU, but I understand the CPU plug goes into the 4-pin socket next to the CPU, which leaves 4 open pins on the main power connector.
Is there a way I can use the Antec PSU on the old HP MOBO?
I wanted to try eliminating either the PSU or the MOBO.

Thanks

FW

 

[ko888]

CONNECTING a 20-PIN POWER SUPPLY TO a 24-PIN ATX MOTHERBOARD

http://www.smps.us/20-to-24pin-atx.html

 

[ultrarunner100]

Ah ha... the computer in question is an HP. Non-standard wiring... so I'm going to leave it alone.
I did get the PSU to power up by shorting the green wire to black (ground), and all voltages were good. I was at first concerned that there was no -5V, but as it turns out, that pin on the 24-pin connector (which corresponds to the same pin on the 20-pin connector) is empty. So it looks like the PSU is good. Now to just find out whether the trouble is just the MOBO, or the MOBO and CPU??