motherboard Wont Power up with new PSU(s)

irishbloke

Distinguished
Nov 6, 2006
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Ever since i got this new motherboard and CPU ive been having a bit of a nightmare with it.

gigabyte ga-ma790fx-ds5 -Latest Bios
AMD Phenom Black Edition 9850, 2500 MHz (12.5 x 200)
4 gigs PC 6400 ram
(Corsair XMS2 CM2X1024-6400 1 GB DDR2-800 DDR2 SDRAM (5-5-5-18 @ 400 MHz) (4-4-4-13 @ 270 MHz)))
ATI Radeon 4870

The problem is that the motherboard will NOT power up at all with the 2 of the latest power supplies i have.

It wont work at all with; (Nothing happens its just dead)
Arctic 600 watt Jeantech PSU (brand new and working)
Corsair 620 watt HX PSU (still to test this PSU in another PC, was about to RMA it but will test it first)

It only seems to work with my Jeantech 450 Watt PSU and i cant for the life of me figure out why. Ive tried everything to get the board to work with the new PSU's. I had thought that the PSUs i got were dodgy but after testing out one in an older PC it worked fine.

Ive removed all parts and tried powering up and i cant get it to boot up. But the PC seems to work fine with the oldish 450 watt PSU which i find just unbelievable.

Can anyone help with this nightmare? Now on the Gigabyte site the CPU i have isnt listed as supported by this motherboard which is kinda worrying could this be the reason? If so how the old PSU boots up.

I just want to have the fracking thing working with the right PSU.
 

auscanzukus

Distinguished
Jul 26, 2008
953
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18,990
Strip the pc down to barebone with only mobo, cpu, gpu, ram, vga & keyb.

Unplug power cord, clear cmos for 10 mins.

Check for extra standoffs on the mobo tray. Double-check these:

CPU FAN
4/8-PIN CPU POWER
24-PIN MOBO POWER

Then try each stick of ram in each slot, starting with the furtherest one.