Mobo powers up without case switch pressed

[W@lly]

Hi there,

I think I have a soon-to-be-dead motherboard [I guess]. It's an Asrock P4i65g with Pentium 4 processor, 2 sticks of 1GB RAM with integrated video.

This mobo is turning on when I switch on the I/O button of its PSU, but won't display POST.

Diagnostics I made/checked;

attached an AGP video card to be used instead of the integrated one

swapped PSU

removed all IDE/data and power cables from optical drives, floppy, hard drives

removed and reseated RAM, + tried new stick

removed CMOS battery

removed all front panel case connectors, but still the mobo turns on when switching on the PSU.


Noticed that keyboard lights turn on [caps,num,scroll locks' LEDS] when switching on the PSU.
Capacitors seems fine, no leaking or bulging.


What do you think?

Thanks

 

[ZenTree]

Try removing the motherboard from the case. Rare but i've had it before where the case was shorting something out on the motherboard.

 

[W@lly]

ok will try and let you know

thanks

 

[W@lly]

Apart from all diagnostics I checked/made I forgot to mention that I have also reseated the CPU as well.

 

[ZenTree]

Oh and any beeps from it? be worth plugging in an external 4 pin speaker in case onboard is broken.

 

[W@lly]

I did a disassembly of the mainboard, and still no success. No beeps, even from an external speaker. Guess it's dead argghh

 

[cyabro]

Caps can go bad and still visually look ok. Only way to really tell is to remove them from the board and test. You can test them in circuit but the readings aren't always correct then.

 

[W@lly]

I never tested the caps, nor removed them
is it worth it fixing the caps?

 

[Rob_NNCC]

No, esp. considering it is not the caps...

 

[W@lly]

it could be that northbridge is not getting enough power (gpu included) that is why I'm not getting a display.

 

[B Trevathan]

removed all front panel case connectors, but still the mobo turns on when switching on the PSU.

Power management option in BIOS set to power on after power failure.

This mobo is turning on when I switch on the I/O button of its PSU, but won't display POST.

Is it not POSTing at all? Did you try different monitor?



Edit:
I didn't mention this before when I posted because I thought it was too basic but then I got to thinking maybe I should have:

Have you checked that the ATX 12 connector is plugged in good?

And also have you checked the USB ports for any damage? maybe unplug them if you can.