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#1
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revive motherBoard hit by lightning?
hi folks,
my p4 is dead following storm.dead as in silent,not even fans. i think it got hit via usb adsl modem (as i have no dial tone either now) and exited into my home LAN via the network card as when i remove this card and switch on the atx PSU fan turn on for 5 sec then shuts down.i have other pcs on this lan (without modems) which wont turn on either but i am not worried about them as they are obsolete. does this shutdown after 5 sec indicate a short on the board? how to i proceed to diagnose the short?would it be near the USB port?anyone ever manage to revive his board?thanks Sam |
#3
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The +5VSB is essential to supporting the "turn on sequence" for the
computer. Without +5VSB, the computer won't turn on. The +5VSB powers chips on your motherboard, and one of those chips controls a signal called PS_ON#. PS_ON# is pulled up with a resistor to logic 1, and when the chip on your board grounds the PS_ON# signal, the power supply then turns on the rest of the supply voltages +3.3V, +5V (main), +12V, -5V, -12V. logic 0 ps_on is a active low |
#4
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In article , "rstlne"
.@. wrote: The +5VSB is essential to supporting the "turn on sequence" for the computer. Without +5VSB, the computer won't turn on. The +5VSB powers chips on your motherboard, and one of those chips controls a signal called PS_ON#. PS_ON# is pulled up with a resistor to logic 1, and when the chip on your board grounds the PS_ON# signal, the power supply then turns on the rest of the supply voltages +3.3V, +5V (main), +12V, -5V, -12V. logic 0 ps_on is a active low Where did I say otherwise ? I said a resistor is used to pull it to the inactive state. That is why, if you sit the PS on a tabletop and plug it in, it doesn't run. Grounding the PS_ON# pin (as you say correctly, logic 0) causes the PS to operate all outputs. Or, for the newbies out there, connecting PS_ON# to one of the adjacent COM pins, because that is less ambiguous. Basically the PS_ON# pin is open collector capable, but not necessarily always driven that way, so don't assume it is safe to short PS_ON# to ground when the motherboard is connected to the PS. Some older motherboards use a 74 series totem pole driver to drive PS_ON#. Paul |
#5
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"Paul" wrote in message ... In article , "rstlne" .@. wrote: The +5VSB is essential to supporting the "turn on sequence" for the computer. Without +5VSB, the computer won't turn on. The +5VSB powers chips on your motherboard, and one of those chips controls a signal called PS_ON#. PS_ON# is pulled up with a resistor to logic 1, and when the chip on your board grounds the PS_ON# signal, the power supply then turns on the rest of the supply voltages +3.3V, +5V (main), +12V, -5V, -12V. logic 0 ps_on is a active low Where did I say otherwise ? I said a resistor is used to pull it to the inactive state. That is why, if you sit the PS on a tabletop and plug it in, it doesn't run. Grounding the PS_ON# pin (as you say correctly, logic 0) causes the PS to operate all outputs. Or, for the newbies out there, connecting PS_ON# to one of the adjacent COM pins, because that is less ambiguous. Basically the PS_ON# pin is open collector capable, but not necessarily always driven that way, so don't assume it is safe to short PS_ON# to ground when the motherboard is connected to the PS. Some older motherboards use a 74 series totem pole driver to drive PS_ON#. "PS_ON# is pulled up with a resistor to logic 1," Not wanting a fight.. was just pointing out |
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