HTPC starts for 3 seconds then shuts down

[Grooby]

Hi

My fairly new HTPC build has been working fine untill 2 days ago. Now it only starts up for about 3 seconds then shuts down straight away and refuses to start again. Turn it off at mains switch and try again, same result 3 seconds later dead.

If i turn off at the mains and leave for about an hour the computer will boot up fine and operate as it should. Shut it down again and try to turn on again and its fails at 3 seconds again. Turn off at mains for an hour again and it boots up ok?????

Somewhat frustrating.

Any ideas?

Thanks
Andy

[Marbles_00]

Sounds like something is overheating, and some protection is preventing it from turning back on possibly. Or could be your PS. Can you replace the PS with another? From there I'd check the CPU Heatsink/fan, and see if it is dissipating the heat properly. Reseat your memory, and all your cards too.

So when powering up...does it get through the POST? Does it beep any error codes? Have you tried to get into the BIOS?

Another check is to take everything out except for the PS, CPU, memory, and vid card and see if you can get into the BIOS and monitor system performance there.

[P3rv3rt B3ar]

sounds like my YLODed ps3... are u sure u dont see any yellow lights

Seriously though, weak or malfunctioning PSU perhaps?

[Grooby]

Does not have time to even start to get through post or beep any errors before it shuts off.

I don't think its the cpu overheating as i would have thought it would crap out all the time, system runs fine once it eventually boots up after being off at the mains for an hour or so.

I suspect it may be the PSU but i will try the memory and sound card resitting, graphics is onboard G45.

Just wierd that it is ok after being off at mains for an hour...

edit - thinking about it at work i suspect it may be the power supply, some sensor must be tripping in the power supply when it starts up. When its powered off at the mains for an hour the supply cools down so when it starts it's not starting from a warm state avoiding the supply tripping???

Andy

[scottw]

Unplug everything connected to the PSU except the mobo and try to turn it on to see if one of your components (HD, cdrom, ...) are causing it.

[Grooby]

Will do...thanks guys

Ok, unplugged everything except motherboard and it shut down again after 3 seconds. So, its either PSU or motherboard i guess?

[dhcf23]

AS previously mentioned the PSU is a the first thing I would try. I had a couple boards do something similar in the past, they were both older socket A boards and they had bad capacitors, one nearly popped off the board. Not sure about your set up but you can check the board and replace bad caps and that can sometimes fix it, good luck.

[lpg]

Man, Had this going on with my wife's Dell she uses for work at home. Had two pwr supplies and two mother boards changed out before it finally settled down. I would try try the powersupply first.

[scottw]

Yeah I was going to say the capacitors next. We use Dell Optiplex's at work and GX270 models had a bad batch that had the capacitor "pop", it would look like an orange or cream colored powder popping out of the top. It was the capacitors right near the cpu. The problem was so bad that Dell extended the warranty for an extra year for that model.

So check closely at all of the capacitors, one or several of them may not be popped yet but may be swollen if you have that problem.

[P3rv3rt B3ar]

Also double and triple check that power switch of the case is connected to right pins on mobo. i will never admit this was explanation behind similar probs for certain master of computer science, and even if it was... it was friend or relative.... very distant relative indeed

[m_ski]

Maybe a fan speed signal has stopped working and you have a critical action setup in bios to shut the system down if fan X stops working. Not quite sure how you test this as you only have 3 seconds to turn it off. Maybe a full BIOS reset will disable the function?

[jji666]

I've seen this before on multiple occasions. Your mobo may be screwed too tightly into the case. Sometimes the stand-offs and screws can short circuit the board. Try removing it from the case or just separating it from the bottom and back plane and see if it will then boot.