Bad Motherboard?

[Lex Luthor]

I have an Ultra 500w ATX power supply that I've got connected to a Chaintech ATX motherboard.

The power supply has 20-pin and 4-pin power connectors. When the 20-pin connector is plugged in only, I get power to the fans (CPU, Case and PSU), hard drive and DVD. When I also plug in the 4-pin connector, the CPU fan turns (sometimes) for a fraction of a second and then the system gets no power whatsoever, not even the PSU fans turn.

I've replaced the power supply so far and the results were identical.

I've also detached all power supply cables from the system devices and removed all add-in cards. I've also cleared the CMOS.

There are no obvious capacitor problems on the motherboard.

Is it most likely just a bad motherboard at this point? With such old system components, I don't think I'd bother replacing the motherboard only. I'd probably just scrap the whole thing (other than the hard drive), so if anyone has any suggestions at all, I'm game.

Any other ideas or other things I can test?

 

[nenforcer]

So the system still doesn't turn on with just the 20-pin ATX connector plugged in?

The 4-pin shouldn't be required for an older AMD system but if the motherboard has it and so does the power supply then you might as well use it.

How about the memory slots? Have you tried with only a single memory DIMM installed, ala single channel?

 

[Lex Luthor]

It's an Intel system.

If the 4-pin isn't plugged in, the CPU fan doesn't start and I'm assuming the CPU probably doesn't start as well.

 

[nenforcer]

Yes if its an Intel system P4 or later with a pin 4 plug on then that must be plugged in or it won't even begin to turn on.

If you've already tried a different power supply then that really narrows it down.

Assuming the CPU/heatsink are mounted properly, have you tried just a single stick of RAM?

Also, does it have onboard video or a discrete card?

 

[Lex Luthor]

Integrated Video.

I've tried it with neither stick of RAM in and it still shorts the PSU with the 4-pin plugged in.

No cards in the system, nothing plugged in. Only thing is CPU and the 2 power connections.

I'll probably take it out of the case just to rule out the case shorting out the motherboard somehow, but other than that, I'm out of ideas and it pretty much looks like the mobo went bad.

 

[nenforcer]

Typically you need at least one memory stick to boot and see something on the monitor or else it won't even attempt to POST.

I assume you have tried it with memory in, though.

Try adding a discrete video card and plug the monitor into that and see if that triggers it.

 

[mrblotto]

So with NO memory installed it presents the same problem?

Typically, if no memory is installed in the mobo, you should at least get some error beeps. To me, it sounds like the 'signal' (for lack of a better term) isn't even making it that far to recognize no memory installed.

It seems to me the only other components left would be the mobo or CPU. It would be far more likely for the mobo to go before the CPU. Good idea to take the mobo out of the case and test it as well.

 

[Lex Luthor]

I think you both (last 2 posters) are missing what I'm trying to say. It doesn't matter what's connected (memory, video card, etc). As soon as I plug in the 4-pin connector, the power supply shorts and stops working.

The motherboard is no longer getting any power at all with the 4-pin connector, so of course it's not going to boot, beep, etc.

If I'm missing something you are trying to say, please let me know.

Still haven't had time to get the mobo out of the case, but I will soon.

 

[mrblotto]

I think you both (last 2 posters) are missing what I'm trying to say. It doesn't matter what's connected (memory, video card, etc). As soon as I plug in the 4-pin connector, the power supply shorts and stops working.

The motherboard is no longer getting any power at all with the 4-pin connector, so of course it's not going to boot, beep, etc.

If I'm missing something you are trying to say, please let me know.

Still haven't had time to get the mobo out of the case, but I will soon.

Gotcha. thx for the clarification. It would seem to me then, since you've changed the PS, only other thing would be mobo short/mobo itself. Good luck!

 

[superunknown98]

Take a good look for bulging or burst capacitors on the motherboard. Those can cause your problem. Otherwise maybe some of the VRM's went bad and the cpu isn't getting enough power.

 

[Lex Luthor]

Take a good look for bulging or burst capacitors on the motherboard. Those can cause your problem. Otherwise maybe some of the VRM's went bad and the cpu isn't getting enough power.

Didn't see any bad capacitors. This was a cheap motherboard originally. I wouldn't be surprised to see it die.

Like I said though, if it's the mobo, I'll scrap the whole system. It's just not worth it with XP, slow/small HD, no discrete graphics, etc.

Last step will be to take it out of the case and try it and also, take the CPU out and see if it still shorts the PSU with the CPU out. If it's a bad CPU, maybe that's what's shorting out the PSU. Very doubtful, but I could probably replace the CPU cheaply and keep the system working.

 

[Cr0nJ0b]

after all you have done, I would say it really sounds like a bad mobo. I've seen some quirky stuff like this before, But it's most likely the board. The only other thing i would do is...

Take out the motherboard, remove the CPU, remove memory, remove all cards and cables, then do one more eyeball check of the motherboard for bent pins, cosmetic scratches on the PCB, cold solders etc...Carefully inspect the CPU socket and pins.

Once you do that, place the CPU back in, carefully...obviously...

Set the BIOS reset jumper and check any other jumpers on the board.

Attach the PSU only with all 24 pins and the power switch cable...You should get the PSU to spin up, and all the fans should start...with some beeps (if there is a speaker attached).

If it worked, put the BIOS reset pin back and restart...then add components one at a time.

If you are still seeing the issue with the PSU not starting...I would say RMA the board and move on.

 

[Lex Luthor]

The verdict is in.

It's a bad motherboard.

I took the motherboard out of the case. The only thing connected as the power button. I took out the CPU as well.

Plugged in the 20-pin and the power came on. Plugged in the 4-pin and power came on for a split second, then shorted the PSU.

Nothing else it can be at this point.

I'll probably scrap the whole system and get something new in the holiday sales.

Thanks all.