Topic: POST Problems

[melmat]

HELP PLEASE

I'm having problem with a PC that at times will not power up. When it works, it works perfectly, but sometimes after being switched off it won't power up again for a while.

I changed the motherboard, the CPU, the case, the power supply and still no joy, its an intermittent problem. I thought it was overheating but the system runs cool, it has a case fan plus the cpu fan (AMD supplied). It never crashes when running, but just refuse to power up sometimes.

specs are

MSI KM2M Combo_l
AMD Athlon xp2000
256 Mb RAM (crucial)
LG CD writer
40gb HDD
windows XP Pro with sp1

[Sandra]

Hi melmat and

If you hadnt had said that you had changed the PSU I would have thought that there was a thermal cutout in that or a surge protection device in it somewhere.
How do you manage to power it up when its having a bad day ?
Do you just keep pressing the power button or do you have to go through some other routine ?
If its just repeated pressing of the power button that eventually fires it up then, the next time it wont power up, (if you are comfortable doing this and I assume you know what you are doing having swapped the mobo etc), you could remove the leads from the switch to the mobo pins and short across them to see if it then fires up straight away, that would indicate a fault either in the switch or the leads from the switch to the mobo  

[ketamininja]

Hmmn, yes that is a strange one. As Sandra said, I have often seen some faulty wires from the power button, as well as the wires not being plugged fully on the mobo.

The button itself may be causing the issue if its cheap and nasty.

Locate the POWER SWITCH connection on the mobo - should be two pins. Remove the wire that goes to the power button.

Use a screwdriver to "short" these pins - effectively doing what the power button does. Its safe enough, just make sure the screwdriver doesn't touch anything else!! Should be easy to do.

If the mobo powers up everytime successfully with this method, then its mos def the wires or button.

If not, then there is another issue! It COULD be related to capacitors on the mainboard, which would be bad news really coz you have to replace....  

good luck

[melmat]

Thanks for replying.

I don't think the problem is with the motherboard, the CPU, the case or the power supply. These have all been replaced and yet the problem still persist.

The funny thing is that the motherboard that I thought was faulty now works fine in another machine and the board I replaced it with which was working ok in the other machine now exhibits the same fault. (the motherboards are identical)

The only things I have not yet changed is the memory the HDD or the CD writer. Could either of these stop a PC from powering up?

I'm thinking of changing the memory next or suicide, lol.

[Sandra]

Its  along shot but I suppose the hard drive or cd rom could stop it if it was demanding more than the PSU could deliver on start up.
The way to check would be again to wait until it wasnt powering up and then disconnect both drives and see if it powered up straight away  

[melmat]

Thanks,

I'll try that the next time it fails to start and let you guys know what happens. In the meantime I'll just keep looking for others who have experienced the same problem although it appears not many have  :'(

[ketamininja]

Yes, any device can stop the system from powering correctly... and it doesn't have to be the power connection that is drawing the power.

Sometimes the data cables (IDE) can cause the issue when plugged into the board - can be the cable itself, or indeed the drive that is faulty, but only causing a fault on the data cable (ie there is still plenty of power in the system)....

happy testing!

[melmat]

Thanks Ket and Sandra for your input but the nightmare continues. Needle and hay stack keeps popping into my head.

I never thought about the cable, I will replace them and see what happens. This is costing me a fortune but I just have to get to the end of this, its becoming personal. lol.