Weird thing

[boston]

Hi!

I've got a weird problem (for me it is) that I wonder if you experts could help me to disentangle.

This is the hardware configuration:
Intel P4 (BX80531NK150G)
2x 256MB RIMM
Ati RADEON 7200 (1.5V)

-installed into-

Configuration1:
ABIT TH7II
Configuration2:
ASUS P4T-E

Symptom:
When the power supply is switched on, the computer immediately starts (!) and runs for about 2 seconds. Normally it would not start until a signal is given to the power switch on the motherboard, right! That's the first symptom that may be an important clue.

Second. When the power switch on the motherboard is put on, the computer starts (the onboard LED is lit, the fans spins etc.), but nothing else happens. No signals, no "POST" codes, no video output.

I have tested the CPU in another computer so I know that is working. The power supply is also working properly. What about the memory modules? I haven't been able to verify they're really working, but the same symptom appears with or without them installed anyhow, so it couldn't be them?! Apart from testing the components (to the extent that is possible for me) I have also cleared the RTC RAM in CMOS, plugged and unplugged the cords, testing each memory module; one at a time. It has shown no progress so far.

The same symptom appears with both hardware configurations.
What could be wrong?

Please help me

 

[batboy]

Have you checked the power switch and reset connectors on the mobo header? Make sure they are installed properly on the correct pins and not shorting out something. Try reseating the main ATX power connector. Make sure you connect the 4 wire square power connector to the mobo.

 

[flapperhead]

if the system is starting on both configurations for 2 secs it is very unlikely that both mbs have the same prob. try this..with the 20 pin atx connector and all other power connectors attached to either mb, pull off the case power button connector from the mb then short the 2 power leads mometarily(on mb very carefully) see if the computer will start. only thing i can think of is u have a bad power button on ur case.

 

[boston]

Thanks for your response.

It seems that these motherboards somehow stores the information whether the power switch previously was on or off in CMOS RAM. When the power supply is switched on, if the motherboard power switch was on during the last operation, the system immediately starts. Thus the 2 second operation was caused by the system trying to run on the 5V standby power!

I had a hard time discovering this since the P4T-E board, which I more thoroughly operated with, has this peculiar feature of a 4 second delay before it enters standby mode. This is not the case with the TH7II which I'm more familiar with. I interpreted this as if the system didn't respond. The fact I used a screwdriver didn't make it easier.

Having solved the first problem the second one was a quite easy nut to crack. I think it was caused by me mistakenly attached the CPU FAN to the wrong connector (they're seated next to each other on the TH7II board), but I'm not sure I did a lot of things... The P4T-E board is probably inoperational.