Power supply problem with SB51G

Hi,

I've got a quit mysterious problem with my SB51G:

If I turn on the PC, sometimes it needs 30 seconds to power on, meaning
for about 30 seconds nothing happens (no fans, no lights, nothing) and
then it powers up, boots and runs without any problem for hours.
Sometimes it doesn't start at all.

I changed the power supply to another one (identical one bought via
ebay) with absolutely no effect. Again, sometimes powering up after
apx. 30 minutes, sometimes refuses to power up.

Both power supplies work correct when shorting the green lead to
ground. Also no problem in the power on switch, since shortening the
appropriate jumper where the "power on switch"-cable ends shows the
same effect as pushing power on.

So, problem seems to sit on the mainboard.

Add. Info: Mainboard is FB51 V1.3. There is a seperate graphics card
installed, but a simple one (Matrox G55 without separate fan). System
worked fine for years.

Any idea? Anybody else with the same problem?
Thanks and Regards
Frank

Eric Parker schrieb:

>
> Maybe you got another duff one on ebay ?
> The symptoms you describe match PSU failures.
> I've now fixed 3 XPC Shuttles with those symptoms by replacing the
> PSUs.
> I've also fixed a PSU by replacing the bad caps. Not economically
> viable in my opinion.
>
> Eric

But why does the PSU start, when shortening the green cable to ground
immediatly. If problem might sit in the PSU, I would expect delayed
start also when shortening the green cable?

Regards
Frank