I'm experiencing an unusual behavior in two of the systems and they seem to both have one common component…they both use the ATX power supply, with the On/Off feature controlled by the motherboard. Both systems are ATX form MOBO's with AMD Slot A Athlon 650 MHz and newer AMD Thunderbird 1 GHz processors. Win 98 SE O/S.

The problem began similarly on both Win 98SE computers when the systems were shut down once and would not reboot. No power supply fan, no processor fan, etc. Also, they won't boot to an emergency boot disk made with Win 98se. There is NO power indication and no beeps or signals.

This problem began innocently enough when I was removing an old hard drive belonging to my Mother that was reporting "hard drive errors" each time the machine booted, asking if I wanted to proceed with boot-up or enter Setup. After some testing and trying to re-detect the HDD in the CMOS, I figured it was easier to remove the drive and replace it with a newly imaged drive. I removed and replaced the hard drive and at that point, I have not been able to boot-up with any signs of power supply or MB processor fans. The Win98se boot disk is not effective.

I removed all power supply leads to floppy, hard drives, CD's and other devices. I removed the expansion cards except the video card and still cannot get power indications. I removed all cables completely from the MB and all devices. I followed the Min/Max Test sequence below:

Startup & shutdown each step - Add components in this order:
MB, CPU, memory, power & MB speaker
Video Card & Monitor
Keyboard
Floppy (check proper connection; tried 2nd connector)
Mouse
Hard Drive (re-jumper to test)
CD ROM
Other expansion cards & devices

I bought a new ATX 300w power supply, followed the above sequence again and that did not fix the problem. At this time, I tested an older "AT" power supply on both systems and both system start to power up and begin the boot sequence. (I didn't finish the boot sequence because the video card was not installed and I was only attempting to start up with power fans on the PS or Processor fan.) This indicated the problem may lie with the ATX power supply and some feature I'm not familiar with regarding the boot up sequence controlled by the MB.

Question: WHY does the ATX power supply not work on two computers using ATX PS?

I suspect it's some little known feature that has escaped me with these two systems that run ATX MB's and power supplies. Remember, the ATX MB and power supply boot up with no off/on button and it's controlled by the motherboard software. I'm open to all suggestions at this point.

Thanks,

Jan Parkhill

your mobo is working with AT powersuply so there may be problem in on/of switch
remove the on/of switch conector from the mobo,then conect the power coard of smps to electric supply then carefuly thoch the powerswitch conector on mobo(with screwdriver).If mobo's ATX system have problem I dont know how it be removed
Best luck

[This message has been edited by UPENDRA UPADHYAY (edited 12-04-2001).]

Thanks for the reply, but I need more ideas. On one computer, the motherboard, processor and power supply were all replaced for testing, giving the same results...

A computer that uses an ATX power supply module has a button on the case that's connected to the motherboard and the button is pressed to power up. UPENDRA UPADHYAY is recomminding to remove the power button's wiring from the MB and momentarily short the MB terminals. If the system powers up, then the button or wiring is bad. Testing the MB or replacing it with a known good one will not reveal a power button or wiring problem.

Also, an ATX power supply module has a 5V circuit that is always on. It is this circuit that enables the MB to turn the PSM on without the PSM itself being on.
Test all 5V connections(red wires) to ground on the ATX PSM. If one of these connections does not show 5V, then the PSM is bad.

Thanks, Ski...

I assumed that was the intent and I'll check that this evening...honestly, I didn't know there was a cable connected to the button anymore...that's my confusion about the ATX PS module since it became popular.

Success....off/on cable wiring (Suspend/Power Switch) running to the motherboard had a short (looks like it got next to something hot and melted insulation). I cut out the bad spot, resoldered the wires, added some shrink tubing and it's good to go again. System #1 is up and running. System #2 gets another close examination tomorrow.

Thanks for the replies and interest.

Jan

Melted or pinched?

If it really was melted I would start checking that machine very carefully...there shouldn't be anything hot enough to melt it. But getting pinched is a good possiblilty since most of the wires are routed in such a way that closing up the case could trap one and then when you tightened the screww to hold it closed could actually damage the wire.

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mjc
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