VOGONS

Mainboard won't soft power on (GA-586STX)

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First post, by MrWeedster

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Hi.

I have a GA-586STX which makes problems with power-on. In 90% of times it won't start with ATX soft power on. In this case i force power on by shorting green + black pins on the ATX power supply after which the board runs flawless. But i have to keep the pins shorted or it will power off again. In the other 10% of cases it powers on just fine, but these occasions get rarer and rarer.
I'd like to resolve this issue and found an old thread on here: Computer Won't Turn On which gave great advice.

I did the same measuring on the ATX connector and have these readings:
(I guess OL means over limit)

20 = 1,2kOh
19 = 1,2kOh
18 = OL
17 = 0
16 = 0
15 = 0
14 = OL
13 = 0
12 = 5,41kOh when measured first and 3,7mOh when measured again
11 = OL
10 = 9,2mOh
9 = 4,3mOh
8 = 130kOh
7 = 0
6 = 1,2kOh
5 = 0
4 = 1,2kOh
3 = 0
2 = OL
1 = OL

I also measured V_Core which is 1,2kOh with or without CPU installed
V_Dimm is 3mOh without and 4,7kOh with DIMM installed.

I just don't know what to do with these numbers. In comparison to the measurements in the other thread i just think pin 10 may be out of range, but i can't interpret these.

Can anybody help with reviving the soft power-on? Capacitors and everything looks good as far as i could tell.

Reply 1 of 2, by Paar

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To be honest, this will probably be too hard to fix without seeing the board personally and measuring it myself. There are a lot of things that can go wrong and if someone is successful in repairing their motherboard, it's not a guarantee that it will be applicable to other one with the same symptoms.

The best way would probably be reading about soft power one and learning how it works. Then do measurements based on this knowledge.

But you can try forcing powering the board on and trying to touch all ICs to check if something is not overheating. Maybe that will give you a clue. Of course this will help only if there is a short circuit somewhere. In case o open circuit, you would need to do proper measurements.

Reply 2 of 2, by snufkin

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5VSB looks like a very low resistance (4.3mohm).

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