Mobo-PSU Fatal Combination

forgotten2 · Post by **forgotten2** » Mon Aug 22, 2005 6:15 am

I have this serious problem.

I have an abit kx7-333R mobo, which has done a great job … now I bought a new psu … Coolermaster 550W.

Now it wont power up with the new psu. The fan on the psu spins up for only half a second and stops running. No action on the mobo exept for the standby power indicator (yellow indicator on the mobo). It lights up so the +5VSB supplies power to the mobo. So when I press the power button the power indicator (green light on the mobo) lights up for a second, also the reset indicator lights up for a second(red light on the mobo), both indicators turn of after less than a second.

My old psu still works with this mobo.

When I took out the Coolermaster and connected it to a new recent mobo it works. So it’s not the psu that’s the problem or my kx7-333R. The problem is when both are connected to each other that gives the problem.

Now, the ONLY difference I can find between these two PSUs is that my old psu has a “-5v” rail. Maybe the kx7-333R needs it for the Power Good Signal so the Power On Signal is sent via the mobo.

I have tried everything and spent a couple of days reading on the internet for similar problems.

Took my mobo out of the case … unplugged all my pci cards, also my videocard, memory, replaced cpu and heatsink, shorted the green wire to any of the black wires in the power connector so it would fire up …. NOTHING seems to be working with this psu attached to this mobo.

I hope anyone can help me to solve this problem.

Abit KX7-333R
Coolermaster RealPower 550W
AMD Athlon 2600+
TWINX1024-3200XL 1GB
Matrox Millennium G400
1x Maxtor Quantum Fireball 541DX
1x PX-708A/UF

vertigo · Post by **vertigo** » Mon Aug 22, 2005 6:44 am

Why did you buy a new psu?

Devonavar · Post by **Devonavar** » Mon Aug 22, 2005 7:47 am

Sounds to me like the motherboard is tripping one of the protection circuits in the Coolermaster. You're best off just returning it as incompatible with your system. It happens from time to time.

I'm also curious, why did you replace the PSU (with that particular model?)

forgotten2 · Post by **forgotten2** » Mon Aug 22, 2005 8:01 am

Tnx for the reply !!

My old psu was dying and had to replace it.
I have also a lot of scsi-devices connected to my system so it needs power.

And yes my KX7-333R is an older mobo (2-3 years). Back then, nobody thought Intel would drop -5V from that ATX standard.

Tomorrow i will return it. Untill that time I am searching for a possible workaround ... if there is one

Devonavar · Post by **Devonavar** » Mon Aug 22, 2005 8:10 am

It's unlikely that the -5V line is your problem. That line hasn't been used for a long time (since ISA slots).

forgotten2 · Post by **forgotten2** » Mon Aug 22, 2005 10:57 pm

If it's not the -5V .... is it possible because the PSU is a dual 12V rail and the Abit regulates CPU power off the 5V rail.

If the CPU regulates it's voltage from the 5V rail, can the overvoltage protection kicking in because of the crossload? The heavy 5V load is probably lowering the 5V below threshold and jacking 12V above threshold and is the combination than possible causing the power supply to trip?

Devonavar · Post by **Devonavar** » Tue Aug 23, 2005 6:28 am

That's a possibility, but the only way to find out for sure would be to actually measure the power being delivered with a multimeter.

larrymoencurly · Post by **larrymoencurly** » Tue Aug 23, 2005 11:52 pm

Is it possible that the CoolerMaster needs a higher load to be applied to it, possibly on only one of the voltage rails?

kesv · Post by **kesv** » Wed Aug 24, 2005 3:14 am

forgotten2 wrote: I have also a lot of scsi-devices connected to my system so it needs power.

You didn't list any of these scsi-devices ?! Anyway, looking at the rest of your components you shouldn't need anywhere near a 550W PSU unless you have 10 scsi harddrives or something like that.

Devonavar · Post by **Devonavar** » Wed Aug 24, 2005 6:35 am

larrymoencurly wrote:Is it possible that the CoolerMaster needs a higher load to be applied to it, possibly on only one of the voltage rails?

Unlikely. You system isn't that low power.

waps · Post by **waps** » Wed Aug 24, 2005 7:51 am

I've heard some more people with the same (i think) problem. It was not with a coolermaster ps but with the sharkoon mutech (the same as the fortron zen)
At the website of sharkoon there is a warning:

--IMPORTANT INFORMATION:

This power supply comes up to ATX 2.0 standard and is not compatible with ATX 1.3 standard and some K8 mother boards.

WITHOUT any problems the power supply fits to all Intel based systems (also ATX 1.3).
--
I think the problem is related to the missing -5v, thats the only thing what i can think of. Did you read in your mobo manual? maybie there is a conection diagram of the powerplug.

Succes!
Maarten