Motherboard Failure?

[ronbo613]

I have an older Intel 875PBZ computer(the one in my sig) that is suffering some kind of major problem. It will not post, no beeps, fans come on, power led is on, no HD activity, the odd thing is it will not turn off unless I unplug it or switch off the PSU so I'm thinking it's either the PSU or motherboard that is fried.
I unplugged the main 24 pin power connector from the mobo and switched the power on and the PSU did not power up. When I plugged it back in and switched it on, the PSU powered up. I unplugged the case power switch from the mobo and it still powered on with the switch disconnected.
So, it's looking to me like the motherboard or CPU is shot, I'm in the process of removing all the boards to see if I get any beeps without the RAM.
Any ideas?

 

[bamaland101]

it sounds like you have some bad caps or vrm's to me..
have you tried all the basics, removing hdd's opticals add on cards and what not?

any caps look swollen or any ic chips look burnt?

 

[ronbo613]

it sounds like you have some bad caps or vrm's to me..
have you tried all the basics, removing hdd's opticals add on cards and what not?

any caps look swollen or any ic chips look burnt?

I did a quick look topside and didn't see any blown caps or visible PCB damage. I'm in the process of removing cards and drives, testing along the way. If everything fails, I'll pull the motherboard and look for problems underneath.

 

[Gorrillasnot]

I'm not sure if I read this part of your post right "I unplugged the main 24 pin power connector from the mobo and switched the power on and the PSU did not power up." but
the PSU receives its signal to power on from the motherboard so unless you had the green and black wire on the 24pin cable jumpered the PSU would not power on with the 24pin cable unplugged from the motherboard.

Best option IMO is to try a different PSU and see if the PC works.

 

[bamaland101]

I'm not sure if I read this part of your post right "I unplugged the main 24 pin power connector from the mobo and switched the power on and the PSU did not power up." but
the PSU receives its signal to power on from the motherboard so unless you had the green and black wire on the 24pin cable jumpered the PSU would not power on with the 24pin cable unplugged from the motherboard.

Best option IMO is to try a different PSU and see if the PC works.

he made me read 3 times over because of that.. didnt know if i was reading right either..
psu is a possibility as ive had some that power the board but wont give it near enough to boot or sound off anything..

 

[ronbo613]

I'm not sure if I read this part of your post right "I unplugged the main 24 pin power connector from the mobo and switched the power on and the PSU did not power up." but
the PSU receives its signal to power on from the motherboard so unless you had the green and black wire on the 24pin cable jumpered the PSU would not power on with the 24pin cable unplugged from the motherboard.

The most prevalent symptom I'm having is that the computer will not turn off unless it is unplugged. I wanted to check to see if there was some kind of short in the PSU or the motherboard. Since this problem only occurs with the PSU connected to the motherboard, it seems there is something wrong with the motherboard that will not allow the power from the PSU to be turned off.

 

[bamaland101]

i personally think its your vrm's buddy. high time for a new board

 

[ronbo613]

high time for a new board

I'm afraid you may be right