Two motherboards, need help to fix them.

[Dan81]

As the title says, I have two motherboards with two problems:
MB 1 - MSI P35 Neo2 - accidentally shorted it and now it won't turn off. It DOES POST though, tested with known good RAM and GPU and got POST. Just the power button does not respond at all. (reset does)

MB 2 - ASUS A7N8X-E Deluxe - southbridge gets hot to the touch (suspecting it dead but not sure yet) but this one DOES respond to the power button and WILL turn off. It does also spin the fans but no beeps, nothing. Just the SB getting hot. (nVidia MCP-T)


Any ideas what to do?

[Dan81]

Re: Two motherboards, need help to fix them.

Answered half of my problem with the A7N8X-E.

ASUS was cheap enough to use LTEC LZP caps on this variant although the VRM section is the same I remembered back on the older one I had - KZGs that ironically haven't died yet.

Now it's ready for a recap. I'm pretty sure the SB gets hot cause of dead LTEC caps. Otherwise it would either not turn on AT ALL (had that happen with a ECS 945PL-A) or would power on as soon as AC is applied.

[stj]

Re: Two motherboards, need help to fix them.

1st one,
check if there is a diode across the switch line that's shorted.

[Dan81]

Re: Two motherboards, need help to fix them.

1st one,
check if there is a diode across the switch line that's shorted.

I'll check although most of that zone is filled with SOT-89 package transistors and a NIKO-SEM driver chip (most likely)

[Dan81]

Re: Two motherboards, need help to fix them.

Replaced the only diode across the switch pins. No dice, same behaviour.

[stj]

Re: Two motherboards, need help to fix them.

diodes would be in 3pin smd packages, you usually find a protection diode between each input and ground.

[Dan81]

Re: Two motherboards, need help to fix them.

diodes would be in 3pin smd packages, you usually find a protection diode between each input and ground.

Yes. I replaced one of those near the PWR_SW pins. No change. The board does the same as before.

There's nothing overheating or anything unusual. Just the board powers on as soon as plugged in. It will work as normal, functions and everything. Just the power button won't turn off the board, requiring to pull the plug.

[stj]

Re: Two motherboards, need help to fix them.

wont turn off at all, or turns off and reboots?
btw, could also be a shorted ceramic cap - meter the resistance of the switch line to ground,5v and 3.3v

[Dan81]

Re: Two motherboards, need help to fix them.

Simply won't turn off at all.

Amusingly, the power switch acts as a 2nd restart button instead of shutting down.

[peterflax]

Re: Two motherboards, need help to fix them.

i have the problem ! havent been able to find the solution just posting this so i can follow this post "ignore me "

[stj]

Re: Two motherboards, need help to fix them.

maybe reseting the cmos settings would help.

[Dan81]

Re: Two motherboards, need help to fix them.

maybe reseting the cmos settings would help.

There's no battery in the CR2032 slot.

[Sparkey55]

Re: Two motherboards, need help to fix them.

There's no battery in the CR2032 slot.

Put a fresh new battery in it.

[stj]

Re: Two motherboards, need help to fix them.

that would help!

[Dan81]

Re: Two motherboards, need help to fix them.

I know what you're both thinking about (Power on AC loss) but that's not the case here, since even then the board should power cycle. Instead, on this one it will not turn off even if I would disable that.

[stj]

Re: Two motherboards, need help to fix them.

i was thinking the ram is full of random crap actually.

[Dan81]

Re: Two motherboards, need help to fix them.

i was thinking the ram is full of random crap actually.

It does this regardless if there's RAM or not.

I tried running the board as bare as I could (CPU and HSF and nothing more) and the same.

As for the RAM, I tested it using a Corsair XMS 2GB DDR2 stick, so not sure if it's crap.

[ratdude747]

Re: Two motherboards, need help to fix them.

I know what you're both thinking about (Power on AC loss) but that's not the case here, since even then the board should power cycle. Instead, on this one it will not turn off even if I would disable that.

Did you try it? Or are just guessing?

I've been burnt by silly stuff like that. Pop in a fresh battery (or one you *KNOW* is good) and try it. Don't make assumptions.

[Dan81]

Re: Two motherboards, need help to fix them.

Did you try it? Or are just guessing?

I've been burnt by silly stuff like that. Pop in a fresh battery (or one you *KNOW* is good) and try it. Don't make assumptions.

Yes, I did try it right now.

Same, it will turn on automatically and never power down.

I also measured the power switches and while the reset gives 0, I get a 100ohm reading on the PWR_SW pins.

[Sparkey55]

Re: Two motherboards, need help to fix them.

Yes, I did try it right now.

Same, it will turn on automatically and never power down.

I also measured the power switches and while the reset gives 0, I get a 100ohm reading on the PWR_SW pins.

Are these ohm readings taken from the switches alone or from the motherboard pin headers? Normally OPEN switches should read as zero ohms when closed (pushed in) and infinite when open (not pushed in).