Need Mac Pro 2009 - 2012 PSU Pin out

[ls1jack]

Sorry to revive a semi old thread. My macpro 5,1 turn on but doesnt chime. I have to try multiple time to power it on ( at least ten) to make it chime and then boot normally. Symptom: kinda power on, fan normal, no keyboard, no chime. I took a couple measurement. Theres the schematic for what I should have, and my own measurement. I know the 12v rail is 12.2 but everything else seem a bit out of spec. So what I'm trying to understand is, if I need a new psu or a new backplane. The psu I got is a delta.View attachment 1717116
View attachment 1717117

Hi, here is a little pic of where the plug relates to the board. Can I not just make a temp switch to jump this to power on the CMP? it should power up but it wont shut down id imagine as it cant drop off my switch when needed, but if you had a switching device on a pcb in this circuit id say the logic board would send a signal down the switching wire to turn it off. I have three boards so I might try this lol Any Ideas?

 

[ls1jack]

That didn't work sorry team!
Back to the drawing board!

 

[yakult121]

Thanks for the information. I just put the PSU on the test bench and shorted the two pins ( must be the "Power On" signal ) out and the PSU turns on. With a fractional load of ~100W on both the A and B outputs, the 12volt rails are stable. Must be a connection, motherboard or front panel issue. Without any of the proprietary ( Not even to developers ) schematics , it is time to get out the DDM and analyzer to see what is not happening. Thanks again. Cheers.

Hello @DrBobF, may I know if you've used ~100W resistors as load?