PC not starting - no m.board beep no video signal

  moohoo 12:19 26 May 09
Locked

Please help!

Recently I've had a few problems with my PC, namely PSU problems and general system instability. I've changed my PSU and reinstalled XP and have half solved my PC instability problem - I'm now only using just 2gigs of ram even though XP used to run perfectly with 4gigs of ram. This solution worked well until today because my new problem is now my PC just won't boot up - there is now no motherboard ready beep or video signal going into the monitor. The PC has power running through it (fans and cd drives are working) but there is no mb boot up sequence so XP can't even start up.

I've tried swapping out the ram and reinserting the VGA card but that hasn't helped. I'm now wondering if my recent system problems have been a symptom of more serious problem, specifically a faulty motherboard.

Thanks for reading, and thanks for any help.

  woodchip 12:25 26 May 09

Looks like the PSU again, or its popped the Motherboard and or CPU. The old PSU may have damaged the mobo parts when it blew. But I would still try a new PSU first

  ened 12:27 26 May 09

What I would do in this situation is start from scratch.

Unplug everything and double-check it is all connected properly.

Have you been removing the cpu. If so check the heatsink is on properly.

Have you tried connecting the monitor to the on board connection instead of the graphics card?

Have you tried a different monitor?

Basically at this stage you need to look at all connections.

  woodchip 12:28 26 May 09

Something to think about, If you have any Hardware like one of your Hard Drives or Optical Drives that is drawing too much power this could blow the PSU, Before Buying anything try pulling all plugs on these drives then try boot to see if you get anything on screen. As one Drive can stop it booting

  ened 12:29 26 May 09

There are two connections from the psu to the board - have you connected them both?

  moohoo 13:04 26 May 09

Thanks for all of the advice. I'll start by looking for the 2nd psu connection first and trying that, and then I'll try disconnecting everything else after that.

I did install a new cpu fan a few months ago, but the temp readings have been ~45 degrees so hopefully that hasn't fried.

I've also tried booting up the PC with 0 ram but that didn't change anything, so I'm sure the ram isn't faulty.

  woodchip 14:04 26 May 09

It will not boot without ram, you have to have at least one stick in. if the mobo as onboard graphics also try plugged into that

  ened 14:22 26 May 09

Try unplugging everything except the main Hard Drive.

A machine of mine blew up recently and it turned out to be one of the expansion cards which caused it.

Took that out and it started immediately.

  keef66 14:48 26 May 09

Saw your other thread and was waiting for this one to appear.

I just went through what you initially experienced: PC needed to be switched on at the wall for a while before the case switch had any effect. Swapping out the psu seemed to fix it, but then it started happening again, and it would take longer and longer to boot. Stripped everything out of the case and noticed a couple of capacitors on the mobo looking like they were on the way out. This made sense of the delayed response to power I suppose.

Replaced the mobo and all is fine, starts first time, every time.

So your suspicions about your mobo may be correct, but the only way to find out is to get hold of another one.

  moohoo 16:52 26 May 09

Ok, so now I think my current psu (2nd one this month) is broken. I can turn on the PC from the case switch but when I try to turn it off from the psu switch nothing happens - the system is still on but the strange thing about the switch is that it feels sticky on the inside. Flicking the psu switch to the On side feels like a normal switch, but flicking it to the Off side I can feel slight resistance, like the button is actually sticky. Has something partially fried my psu?

I've also unplugged components like hdd and cd drives and my vga card but the PC still won't boot. I'm going to start unplugging the sound card and wifi card as well, but I really doubt that these cards are causing my problem. :/

I've also tried another psu from another PC but the problem is still the same as before: my PC won't boot.

keef66, my replacement psu didn't have any charge problems unlike my 1st psu or both of yours. I think I will take a look for burnt capacitors though, but where are they situated? I really hope I don't have to replace my motherboard.

Thanks you all for your help though.

  ened 17:12 26 May 09

You shouldn't be starting your pc from the psu switch.

All that switch does is make the unit live and able to be turned on. Like plugging a hoover into the mains. It needs to be turned on by the switch on the front.

Given that you have tried another psu this sounds as though you should check you don't have a graphics problem, either the card ot the monitor.

With everything disconnected (including the HDD) you need to plug the monitor into the onboard graphics and turn it on at the front (I repeat: the switch on the back will not turn it on).

I take it you have checked the monitor is turned on?

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