System wont post

older system moved from one case to a box back to old case when i got new one for main system.

mobo is a7n8x asus cpu is athlon xp 1800?? its been so long ..

the system turns on the cpu fan spins up then turns off right away and never starts up again. the green light on mobo stays lit but nothing else happens.. heres what ive done

i reset cmos even replaced battery

i removed all hardware but cpu and heatsink still nothing

psu is antec 450w .. only thing im left with is mobo or cpu is fried so i came here
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More about system wont post
  1. Please perform every step in the READ before posting about boot/no video problems! sticky at the top of the forum. It was created to troubleshoot this exact type of problem. It's likely something's either shorted out or you forgot to plug something in since it quit working when you moved it from one case to another.
  2. i went thru that and i even removed the ram im not even getting a beep from the speaker with no ram in it

    would like to add i tried booting this with just a psu and mobo on my workspace just to make sure it wasnt the case shorting it somehow
  3. Try to borrow a known good PSU. Or better yet, see if you can test your PSU in another working system. If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
  4. sorry took so long to reply, real busy this time of year at work. psu is fine i just rebuilt another system using that psu and its running fine. now the problem i have is that is it the cpu or the mobo and how to tell.
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