ASUS M4A88T-M LE & Cooler Master 500W PSU fails

So I am struggling with either a design flaw or a two bad PSU's or Mobo's.
I am following the troubleshooting tips and am breadboarding this out of the case - Mobo, CPU & PSU only. Maybe I am missing something else.

I have confirmed CPU & CPU Fan in a seperate PC.

In all three configurations - PSU1/Mobo1, PSU2/Mobo1, PSU2/Mobo2 - I get no fans spinning in either the PSU nor CPU fan. Mobo power LED is on.
No system beeps either.

When I disconnect the 20 pin harness and leave the 4 pin in the 24 pin connector, and then jumper the PSU Good signal on the 20 pin harness, both fans come on.

I find it difficult to believe I have gotten two bad Mobo's with the same failure mode. Many people on the egg have very positive experiences with both the PSU & Mobo.

I get the same symptoms with a memory stick and graphics card installed.

Here is my questions.
1. I am considering measuring the resistance between the PSU good and ground on the backside of the mobo where the connector pins come through. SHould I see continuity always or is that a switched circuit from some other part of the mobo
2. If all else fails would you try a different PSU vendor or Mobo Vendor? My preference is PSU as its cheaper :).
3. Any other suggestions / checks gladly welcome.

Target system.

Mobo - M4A88T-M LE
CPU - AMD Phenom II X4 945 Deneb 3.0GHz Socket AM3 95W Quad-Core Desktop Processor HDX945WFGMBOX
Cooler - Stock cooler with artic silver paste
PSU - COOLER MASTER eXtreme Power Plus RS500-PCARD3-US 500W ATX12V v2.3 Power Supply
6 answers Last reply Best Answer
More about asus m4a88t cooler master 500w fails
  1. CM eXtreme power plus PSU's are not know as quality units.
    I'd recommend something from the Corsair, Seasonic, PCP&C, Antec or Enermax lines.
  2. ^+1
    What he said.
  3. Best answer
    Have you made sure to plug the 4-pin Molex connector 12v cable into the mobo next to the DIMM slots?
  4. Thanks for the answers. I have plugged the 12V into the CPU power connector, per the manual. There is no other plug nearby (or on the board for that matter).

    Does the Mobo circuits or BIOS check for something besides the presences of cpu, cpu fan, and PSU good prior to starting up? Based on the troubleshooting steps suggested, it appears that is all that is required to switch on the voltage rail connections within the mobo.

    As to the quality of the units, I checked the PSU pins and they all had valid voltages. Perhaps they can't source enough current but that is a unlikely failure mode.

    My next cumbersome step is to validate the PSU in my other computer and then try the other computer PSU for the mobo.
  5. I painfully learned that the Mobo needs the power switch pins connected to the case switch or something similar. Both units fired up just fine. I have submitted a suggestion to the moderator to change the troubleshooting guide to include connecting the pins to the switch....
  6. Best answer selected by lrogers287.
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