Electronics > Repair

unusual computer motherboard issue.

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Dump the CMOS RAM and compare. You may have an unusual issue but this is by no means an unusual/rare chipset. NM10 was used in plenty of computers when it was new.

@perieanuo - sorry, I should have clarified. typically this board is powered by an external 12v power supply. (actually a power supply that supplies 12v and 24v.) the AC power switch simply powers on the external power supply, that in turn powers the computer board, which in turn (when it works) turns on due to the BIOS setting on AC power loss which would be set to on.

when the computer stopped powering on automatically, as it should, I programed a microcontroller to wait until the computer did it's initial power on and subsequently fail... supply a low signal to the PWRBTN front panel header (normally unoccupied) to power on the board.

except it seems to randomly automatically power on as it should, but doesn't stay powered on when it does.
when forced on with the PWRBTN header, it runs and operates just fine.

if it weren't for it randomly working and "properly" powering on like it should, i would just stick with the microcontroller turn on.

I've checked the power supply for ripple and low voltages, but everything is tip top...and can confirm that his issue is isolated to the motherboard itself, as this is a known issue with these boards. (we have had 4 other replaced by the company under warranty but his system is no longer available to us and the service depot refuses to work on them.)

@amyk - I am in contact with the first party company who supplied the system to see if i can get a known good copy of the flash, as it's a customized firmware for that company (boot logos etc) and it wouldn't match with the bone stock MX280 firmware as supplied by BCM anyway. i'm tempted to just flash stock firmware to the BIOS, but i suspect the software may no longer work...this company has a tendency to do stuff like that. i have another computer form this company that will not boot with anything but a western digital brand harddrive installed. all other drives (and even no drive) say that an unauthorized harddrive is installed... and this is in the BIOS before it's even booted.

I'm still of the opinion that this is a hardware, not software, fault. I'd measure the voltages on the power button pins and see if something is somehow activating it randomly. If a pullup/pulldown is bad, you can see this sort of behaviour.

ok, it's clear now
so maybe you don't need a micro to start this when 12Vdc comes in, maybe just a big capacitor will do. finally, until you find the fault, this will be the same as your existing delayed powerbtn solution
try to rewrite the bios, i saw they offered some bios updates at the time, maybe try some alternative bios if you can write the bios in external programmer to be safe (saving this existing one first)
bon courage


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