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  Motherboard boot problem 
 Date Written 
Graham Strong May 29, 2015, 06:58am EDT Report Abuse
Hi Guys,
I have a strange problem with a motherboard from Acer SA90 MB code F671CR.
MB is out of the case with minimum hardware attached.
Power on button does not switch on, shorting the two pins also no boot yet switch is ok (continuity tested).
Now the strange part, if I hot-wire the PSU power plug (green & black wires) it boots fine. At first I could remove the link after booting and it still powered. If I hold the power button for 4 seconds it switched off!
Now though removing the (hot-wire) link shuts everything down.
Tested with another PSU no change to issue.
Found three capacitors with domed tops, replaced those but still no boot from power switch alone.
Seems strange the switch off worked but not switch on?
Any ideas, or is it a dud MB?

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Naveen Goud Jun 01, 2015, 01:03am EDT Report Abuse
>> Re: Motherboard boot problem

I think, instead of meddling with the mother board, it will be better to ask for a replacement.

Otherwise, it will be prove as simply a time waste and money waste situation.




Graham Strong Jun 03, 2015, 08:19am EDT Report Abuse
>> Re: Motherboard boot problem
Can't ask for a replacement as it's several years old and if I didn't take it would have gone to the in-fill site. As regards to wasting time, I get a kick out of getting dead stuff working again, so happy to continue.:)

Is it possible to get a circuit diagram of the MB?
In particular the part which takes the on/off button and makes the PSU switch on.

I'm considering a transistor (4-5 secs) latch circuit add-on, as once the green & black wires are shorted for a few seconds it works fine and from then on can switch off after pushing the button for 4 secs if needed.

Any clever electronics guys have a simple circuit. Can run off the 5v rail as it's always available. Got a boxful of transistors from the 60 & 70's.



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