Troubleshooting dead system: CPU or motherboard?

rtsai · Post by **rtsai** » Mon May 30, 2005 3:39 pm

In this thread I described a problem I had with my PSU. I RMA'd it and received a replacement from Seasonic. The RMA went smoothly (aside from waiting for coast-to-coast shipping, which can't really be helped), and I've determined that the new PSU should be OK (paper-clip connecting green and black wires allows PSU fan to spin up).

But the system still won't boot

. The relevant components: Soltek SL-K8TPro-939 motherboard, AMD 3500+ 90nm CPU, and Seasonic Super Silencer 400. I think I was extremely unlucky and experienced simultaneous failure of PSU and motherboard.

I discovered that when I connect the 4-pin +12V CPU cable to the motherboard, the PSU fails to power on and the computer fails to boot. If I unplug this single +12V CPU cable from the motherboard, the case fans spin up. I have not experimented with plugging in disk drives to see if they also power up, but I believe that this is sufficient evidence that the motherboard and/or CPU is defective.

So, given the above description, is it possible to determine whether it is the motherboard or CPU that is defective? Do you need more information? At this point I believe it is the motherboard, so I will be RMA'ing that with NewEgg.

Thanks.

frankgehry · Post by **frankgehry** » Mon May 30, 2005 5:37 pm

I couldn't follow the old post very well, but do you have a 20 pin atx connector on the ss 400 and a 24pin mb connector and you use an adapter to go from the 20 pin psu to the 24 pin mb. You don't need the adapter. Just plug in the 20 pin atx cable into the mb. You can research this if you'ld like but according to my asus instructions and antecs website the adapter is not necessary.

Your psu seems to work. The cpu fan comes on when you unplug the extra 4 pin connector. Now what happens when you don't use the adapter and just use the 20 pin atx cable from the psu. Its a little hard to follow everything that you've done, but I wouldn't stop trouble shooting yet. - FG

Be sure and shut everything down before you reboot. Turn the power supply off for a few seconds.

EDIT: NEVER MIND

m0002a · Post by **m0002a** » Mon May 30, 2005 5:42 pm

frankgehry wrote:I couldn't follow the old post very well, but do you have a 20 pin atx connector on the ss 400 and a 24pin mb connector and you use an adapter to go from the 20 pin psu to the 24 pin mb. You don't need the adapter. Just plug in the 20 pin atx cable into the mb. You can research this if you'ld like but according to my asus instructions and antecs website the adapter is not necessary.

Your psu seems to work. The cpu fan comes on when you unplug the extra 4 pin connector. Now what happens when you don't use the adapter and just use the 20 pin atx cable from the psu. Its a little hard to follow everything that you've done, but I wouldn't stop trouble shooting yet. - FG

Be sure and shut everything down before you reboot. Turn the power supply off for a few seconds.

The Soltek MB in question has a 20 pin input connector from the PSU.

thetoad30 · Post by **thetoad30** » Mon May 30, 2005 7:52 pm

Here's an idea: Go to any CompUSA or Circuit City, or a Fry's Electronics and get yourself a power supply tester. This thing has a hefty resistance on it that will more than load a PSU, and that way you can tell if its because of the PSU or if you might be jumping the wrong pins, or if you just aren't loading it enough. I know its a "cheapskate" way out, but trust me, it will tell you in no time what the problem is. (I read your other thread).

In this problem, it seems to me that your motherboard is causing the problem. Returning a motherboard is A LOT easier than returning a CPU, so I would, if it gets down to it, return this item first.

Just some obvious things:

Make sure the CPU isn't damaged in any way. Check the core if it has one open (I'm not an AMD user so I don't know if they have the heat spreaders on them yet or not).

Also, check to make sure all the motherboard jumpers are in their correct places, and make sure you have the switch connectors, the USB connectors, the HDD LED and power LED connectors either completely off the motherboard or they are correctly placed.

Next, make sure the Clear CMOS jumper is in the correct position. I have seen sometimes where the system will do exactly what you are describing because the individual forgot to put the jumper back to the "parking" position after using it because the computer froze from their BIOS settings.

Just some thoughts.

Mats · Post by **Mats** » Mon May 30, 2005 7:58 pm

...and check the HD and floppy connectors. Especially the floppy if you have one, I think someone said that his PC wouldn't boot if the floppy signal cable was upside down.

rtsai · Post by **rtsai** » Tue May 31, 2005 3:44 am

I've done all the troubleshooting and double-checked all the headers and feel better that we've arrived at the same conclusion of implicating a bad motherboard.

This is my first system build. While this has been a very rewarding experience (it's only a PVR box, so it's basically a "play" computer that I don't critically need), it's been good to know that I haven't done anything completely wrong along the way, both when building the initial system, and when troubleshooting stuff when things go wrong.

Thanks!