Desktop PC - No Power

[Bootman 650]

I am ripping my hair out with this one.. Job came in earlier in the week with the problem - NO POWER!

Since then I have ...

Tested PSU + Tried Alternative PSU
Checked Power Button still functional on case.
Tested Memory + Tried alternative memory
Tested CPU + tried alternative

Ordered a replacement board...

Problem still persists with all alternative parts. How weird is this? I am losing my mind.

Any help would be awesome!

 

[PBComputer]

Have you tried it outside the case on just the bench?
Different Power lead?
Cleared CMOS?
Is there a reset button on the board (I have seen a few need it pressed)

 

[lcoughey]

Did you turn on the power bar? Just to confirm, when you push the power button on at the front of the case, nothing happens? No LEDs, no fans spinning, nothing?

When you power it on, is everything disconnected? My gut instinct is saying that the hard drive has blown electronics, but I really don't have enough information to go on.

 

[Martyn]

It needs to be a bit more clearer when you say no power as previously said. List what is and isn't working and we can move on.

 

[Rayspcsolutions]

Check the standby power voltage from the PSU (purple wire I think) some computers if that voltage is out of range (5% of 5v) it will not let the computer power on.

I know you said you used an alternate PSU. I suppose it is possible the alternate could be out of range also.

I ran into this issue only once on Dell plugged in a PSU tester and all voltages showed fine except that the standby voltage showed 5volts but it was blinking. Tested with DMM and the actual voltage was 4.5v, all other voltage tested out fine with the DMM. Put in a new PSU and the computer fired right up

 

[Mainstay]

Have you tried it outside the case on just the bench?
Different Power lead?
Cleared CMOS?
Is there a reset button on the board (I have seen a few need it pressed)

yeah - I'd say there is a grounding issue. the system is shorting. try on wood.

 

[nlinecomputers]

As suggested you need to get everything out of the chassis and test it bare on the bench. You may have short to ground in the chassis. Before doing that I would try and boot with as bare minimal system as possible. Only a keyboard and video. No HDD or DVD/CD player hooked up. On board video card if you can.

 

[4ycr]

Have you checked to make sure nothing is touching the motherboard from below it? I had one that built their own computer but didn't use any standoffs, it worked for a moth before shorting.

 

[cypress]

Grounding issue sounds like a good bet.

 

[tek9]

Did you try to short the power on lead and a ground wire on the motherboard main connector? I had a brand new Dell XPS out of the box that wouldn't turn on. Turns out the power button connector was dead. Bypassed it with a Radioshack push button and it worked.

 

[mr m]

I see that you swapped the mobo but have you checked the external ports for bent/mangled pins. I had a few bad USB ports that caused this same issue. Don't forget to disconnect the memory card reader if one is installed.