Hi,
I have a troublesome motherboard. It will not start. PSU I believe is OK, and have swapped for like PSU and system still fails to power up, leading me to believe its a motherboard fault.
No activity from power switch invokes the PSOK/PON line on the ATX.
If I short the ATX green line to GND (for PON), the CPU and PSU fan spin briefly, then stop. There is a constand 5VSB line from the PSU into mboard.
It is very difficult to trace anything on the mboard, but I have found what I think are two suspicious things;
1) the 3.3v lines on the ATX connecter on the mboard all seem to be grounded - the 5V and 12V lines are not - I assume this is incorrect.
2) I have found a SOP-8 chip that seems to have two grounds, one on pin 5 which is correct, and also on pin 7, which is supposed to be the VOut - I assume this is incorrect? This is close to the USB pin outs section.
I dont think the two can be tied together - a vout and 3.3 line in would compete, so is there something common that could link the two which could be grounding them?
Regards
Jason
I have a troublesome motherboard. It will not start. PSU I believe is OK, and have swapped for like PSU and system still fails to power up, leading me to believe its a motherboard fault.
No activity from power switch invokes the PSOK/PON line on the ATX.
If I short the ATX green line to GND (for PON), the CPU and PSU fan spin briefly, then stop. There is a constand 5VSB line from the PSU into mboard.
It is very difficult to trace anything on the mboard, but I have found what I think are two suspicious things;
1) the 3.3v lines on the ATX connecter on the mboard all seem to be grounded - the 5V and 12V lines are not - I assume this is incorrect.
2) I have found a SOP-8 chip that seems to have two grounds, one on pin 5 which is correct, and also on pin 7, which is supposed to be the VOut - I assume this is incorrect? This is close to the USB pin outs section.
I dont think the two can be tied together - a vout and 3.3 line in would compete, so is there something common that could link the two which could be grounding them?
Regards
Jason
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