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- Posted on
March 12, 2007, 9:03 pm
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When i connect the power supply to motherboard, the motherboard turn
on right away(fan spin) without pressing the power-on button. And
there're nothing shown on the screen. .
I clear the cmos, reseat, replace the ram and CPU ;and it's still the
The moterboard uses ATX power , but layout is proprietary(lay out is
completely different from the normal ATX) and it is impossible even to
obtain a used one.
Can anyone give me a hint on what parts of component should i start
Re: Motherboard connects to power supply, keep on(fan spin) forever?Repair a proprietary motherboard
Since it is proprietary, it could be all that much more
important to tell us as much as possible about it.
Don't connect the power supply to the motherboard while the
power supply is already connected to AC. Are you sure you
are able to work with this system safely if you aren't
keeping it unpowered until reconnected, or am I
misunderstanding what you wrote?
Some motherboards will do this without it being a sign of a
problem, particularly if the board bios was set to (or
defaults to) last powe state, meaning that it remembers it
was turned on and will turn itself back on deliberately
until turned off properly. You should ignore that it's
doing this for the time being but unplug AC and clear CMOS
at this point (or pull battery for 10 minutes, also while AC
power is disconnected from PSU).
You might also try the reset button, or if this proprietary
system has none, locate the reset pins on the motherboard.
What is the history of the system? How long had it ran
without issues, what was the suspected cause of failure, how
long since it has ran? Do you know for certain that any or
all other parts are working still? Check the battery
voltage, a low battery can cause this without any other
problems, depending on how the board was designed.
So are you sure all these other parts work? Were they the
same parts that were previously working in this board, and
you have taken them out and tried them in another system to
confirm they still work?
Playing odds (no guarantees), unless there was overt
physical damage or a fan failure, it's usually the
motherboard or PSU that fails first.
Disconnect the PSU and check the voltages while powered by
shorting the PS-On pin to ground. If it won't run like that
it may need a load on 5V rail, maybe 12V rail and
occasionally 3.3V rail too. Examine the board for obvious
signs of problems like discolored copper (overheating), flux
seeping out around mosets, burn holes in chips, cracks, and
especially capacitors venting/leaking/etc.
We don't know much at all about this system yet, except that