PC not powering up properly. a judder then nothing...

[Paladash]

Hi Guys,

I'm just in the process of building a new system. Have installed the CPU and cooler on the mobo, installed the RAM and have screwed the mobo into the case. The PSU has been wired up to the mobo and all connections have been made.

I haven't installed the g-card or s-card or even monitor yet; just want to check at this stage that the system powers up OK.

I plug in the PC P&C 750W into the mains (I'm in the UK but the PSU has PFC which, according to their site, means it can run on any input voltage between 90 and 246V <we're 240V>), switch the PSU on and then turn the PC power button on and ...

... the system makes a single 'judder', the fan(s) light up for a brief moment and there's a single twitch of the fan blades, then everything goes quiet; no movement or sound. If I leave the system powered on in this state i get this 'judder' every, say, 5 seconds but nothing happens. Obviously not working.

I've pulled out and re-plugged the power connectors to the mobo and fans, etc, but still get the same. Even turned the 2 pin 'power on' lead (the one linking the PC power on button on the front of the case) 180 degrees just in case that had something to do with it. Tried again but same judder.

Does anyone have any suggestions please?

Really appreciate your help.

thanks.

 

[Zorg]

My guess is that you have a short somewhere. I wouldn't leave it plugged in and let cycle that way. That is a single rail PSU so it delivers a lot of current. I know this is a pain in the neck, but remove the mobo and power it up on a piece of cardboard etc. Check standoffs, wiring etc. for a short.

Oh, and look for burn marks.

 

[Paladash]

thanks Zorg.

Also, is it possible that the mobo is either (a) DOA or (b) I've somehow broken it while doing this install

 

[Zorg]

I added to my post, look for burn marks.

 

[evongugg]

Do you have any extra standoffs screwed in?
if so remove the extras, they short the motherboard.

 

[Paladash]

Hmm. interesting... don't think so. I must admit, I can't remember how many screws fixed-down my old mobo; I thought it used all the screws but may be wrong. Certainly all the stand off screws have screws in now. As all the fixing screws were mixed and matched I can't tell how many I used the first time around

 

[warezme]

Zorg is correct, sounds like a SHORT,

Unplug everything, all drives, CD, floppy if any, everthing, cept motherboard, when it comes up, shut down and start plugging things back up, one at a time. If yours is a high end card, make sure you are using the correct power hookups also.

 

[Paladash]

thanks Guys. I'll give this a go!

 

[GuyAmI]

Maybe consider the motherboard as the culprit.

I've seen it before where everything else on a system was fine, CPU, memory, PSU, video, everything else was fine except that the board was done in. When a power up was attempted, the fans would twitch, then nothing. Silence. Problem was eventually traced to the board itself as being shot.

Just something to consider.

 

[Paladash]

Thanks guys. I had a 3rd-party check it out and it seems as though there's a power distribution problem on the board. Various PSUs were used and, in each case, there was an issue when the CPU connector was connected to the mobo. Oh well, back it goes. Hopefully the replacement will be better!