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PC wont POST

by vwj4786 / April 11, 2005 9:57 AM PDT

I took the motherboard and processor out of a working pc to repair another pc. To repair the pc I robbed I purchased
ABIT SG-72 v1.1 motherboard
Intel P4 3G 800 mhz
512MB 3200 DDR (Bravo)
new mb has onboard ethernet, sound and video
PC was running WinXP pro w sp2 but that is not material as bios does not load.
When I power on computer the power supply fan (PowerMax ATX switching 400 watt), cpu fan and case fan all come on and stay on. No power led, nothing else. I get no beeps. I have rechecked all connections - now all drives are unplugged, the only things plugged in to motherboard is cpu with heatsink/fan, memory, case fan, leads to case speaker, pwr led, hdd led, reset, pwr sw. Switch will turn power on but not off and no leds light. What have I done wrong?????? Thanks

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Any chance that when you mounted the
by Ray Harinec / April 11, 2005 10:33 AM PDT
In reply to: PC wont POST

new mobo that you left a hex standoff there that didn't line up with a mounting hole of the new mobo. That is frequently done and shorts some artwork circuitry, sometimes irrepably damaging it, others just prevent it from running.

The next test is to mount the mobo on a large piece of cardboard, isolated from everything.

As for turning off with the switch, it may require holding the power button depressed for 5 seconds.

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mb on cardboard
by vwj4786 / April 11, 2005 12:15 PM PDT

It doesn't matter how long you depress the power button, it doesn't turn off. Explain mount mb on cardboard please. Just remove from case, place on cardboard and hook up power supply? And I did remove all stand offs not used and added two spacers where holes did not line up. I thought if the board were shorting out it wouldn't power the fans - not true?

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The LEDs not lighting is most
by Ray Harinec / April 11, 2005 10:39 AM PDT
In reply to: PC wont POST

likely that the two leads are reversed. They are diodes and they must be connected with the proper polarity for them to conduct and illuminate. Having them wired backwards does not hurt them.

The Power Switch and reset switch are not polarity sensitive.

The case speaker can be iffy some mobo use pins 1 and 3, others use 1 and 4.

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by vwj4786 / April 11, 2005 12:20 PM PDT

The book with the MB labels the pins, so HDDLED is 1&3 and it is easy to figure out which are 1&3 BUT I don't know on the leads which is 1. My 1st guess was that the ^ was pointing to pin 1. However, when you get to 2&4 is the ^ pointing to 2? So when it didn't work the 1st time I reversed them all - and they didn't work that way either. (sigh) Also, I tried orignally plugging speakers into the built in sound board - no beeps.

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PC won't POST solution
by vwj4786 / April 21, 2005 10:15 PM PDT
In reply to: PC wont POST

For anyone wondering, I did not have the CPU locked in. Lift the little bar, put the chip in, lower the little bar. That's what being in a hurry and failing eyesight gets you - frustration. Found some reading glasses and figured out the power led is not going to work as it has 3 pins and there are only 2 pins to plug into on mother board. Once the CPU was locked down everything else was great.

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