MSI N1996 wont boot (in a normal way)

[blimb]

Hello,

I am having a problem with my current very old motherboard, an MSI N1996. The problem comes down to this:

-Yesterday there was a powercut, and afterwards my pc did not turn on. There is absolutely no sign of life. No Power LED, no fans running, nothing.
-First thought: PSU died (or fuse blown, etc). On inspection, by shorting the green and black wires, the PSU turned out to be running just fine and delivering the correct voltages
-Second thought: maybe the CMOS battery? Took it out, checked the voltage, which is correct and put it back in.
-Then I removed the motherboard and the PSU from the case and put it on the table. Got a multimeter and started measuring.
-Found out that there is no voltage on the +side of the power_on switch header, and that it is connected to the ground
-Found out that there was a 5V on both the + and the - of the power_LED header (which would explain no LED, and im not even sure thinking back that it was always lit even if the pc was off..)
-If I connect one of the 5V from the power_LED header to the - of the power_on switch, the motherboard suddenly boots!

So, I could of course just forget about the powerLED and connect the power_on_switch in a weird way, or just get a new cheap motherboard, but I would like to know what is going on (even if just out of mere curiousity!).

So my questions are... Electronically speaking, how is the + of the power_on_switch header supposed to be connected? is it supposed to be connected (directly?) to the standby voltage? Is there anything on the board which could malfunction making a short between the + and the ground? How is the power_LED connected electronically?

Thanks for reading and hopefully someone will have an answer!

 

[PIEapple]

-If I connect one of the 5V from the power_LED header to the - of the power_on switch, the motherboard suddenly boots!
It's seems like your case power_on switch is dead? try to use pen to boot your pc(use pen to touch mobo power_on switch),that you will know what happen.

 

[blimb]

Hi PIEapple,

Thanks for your answer. Maybe I wasn't completely clear. I'm already running the mobo completely isolated on the table. The only thing connected is the PSU to the mobo. Now, let's look at the mobo pins to the front, and lets call them:

1: PLED+
2: PLED-
3: PSW+
4: PSW-

If I measure the voltages on these pins (with the PSU in standby mode) they read:

1: 4.7 V
2: 4.7 V
3: 0 V (and this pin is directly connected to ground if I check with my multimeter)
4: 0.7 V

Thus, if I connect the PSW+ to the PSW- (which should normally boot the machine), nothing happens because pin3 is actually 0V! However, if I connect either pin1 or pin2 to pin4, the mobo boots.

So I'd like to know how these pins should be connected internally, on the mobo. Are they just supposed to be hooked up to the standby voltage? or are there any components in between, which I could maybe replace?

Thanks,

 

[PIEapple]

Hi PIEapple,

Thanks for your answer. Maybe I wasn't completely clear. I'm already running the mobo completely isolated on the table. The only thing connected is the PSU to the mobo. Now, let's look at the mobo pins to the front, and lets call them:

1: PLED+
2: PLED-
3: PSW+
4: PSW-

If I measure the voltages on these pins (with the PSU in standby mode) they read:

1: 4.7 V
2: 4.7 V
3: 0 V (and this pin is directly connected to ground if I check with my multimeter)
4: 0.7 V

Thus, if I connect the PSW+ to the PSW- (which should normally boot the machine), nothing happens because pin3 is actually 0V! However, if I connect either pin1 or pin2 to pin4, the mobo boots.

So I'd like to know how these pins should be connected internally, on the mobo. Are they just supposed to be hooked up to the standby voltage? or are there any components in between, which I could maybe replace?

Thanks,

Do you have other case?Try to use ohter case header to connect the mobo pin.
I don't know what happen,but the old mobo don't have fuse,when you get a powercut,always get some weird problem.
So..If you can boot,I would say you are so luck~

 

[CompGee]

Your motherboard is REALLY messed up...