Newly built PC, problems

[Gradient]

I connected up the components for my new PC, checked everything was connected properly, and turned it on. Early signs were good; it powered up fine, the audio worked, and it seemed to recognise all my hardware. I managed to get into the BIOS, and I quit and powered down without changing anything. The only thing I changed before powering up again was to move a cable that was obstructing a fan; when I turned on again, all I got was a blank screen; no start-up beep, nothing. I've tried resetting the CMOS by switching jumpers about and even by removing the battery, but neither has worked.

The last time I turned it on, it powered down, powered up, and continued to do this over and over, with the intervals between power downs getting progressively smaller. I'd say this was a fault with the CPU, and it wouldn't surprise me as I was the one who fitted the heatsink and fan, but it was on for minutes the first time it powered up with no problems, and the heatsink seems to be fitted in place absolutely fine. Any idea what might have happened?

Thanks,
Phil

EDIT: Specs are as follows:

Asus GeForce EN7300GS-HTD 256MB DDR2 TV-Out/DVI (PCI-Express) - Retail
OCZ 4GB (2x2GB) PC2-5400C5 Dual Channel Vista Upgrade Gold Series DDR2 (OCZ2VU6674GK)
Intel Core 2 Quad Pro Q6600 "Energy Efficient SLACR 95W Edition" 2.40GHz (1066FSB) - OEM
Samsung SH-S203NBEBN 20x DVD±RW SATA Dual Layer Lightscribe ReWriter (Black) - OEM
Samsung SpinPoint T 500GB SATA-II 16MB Cache - OEM (HD501LJ)
Enermax Noisetaker 370W EG375AX-VE(G) SFMA ATX2.0 PSU
OcUK Value IP35 Pro Intel P35 (Socket 775) PCI-Express DDR2 Motherboard

 

[mailpup]

Try booting with only one RAM module in place and then shutdown, switch and boot again. Perhaps one of the RAM sticks is defective. If so, you'll have to return them as a set.

 

[Gradient]

I've remembered something else; after I exited the BIOS, I had a message saying 'Warning! CPU has been changed", or something similar. I googled it and this thread popped up:

https://www.techspot.com/vb/topic20269.html

so it's probably either the RAM, or I've buggered up the BIOS somehow. I'll try what you suggested and see what happens.

EDIT: It's not the RAM. Suggestions on resetting the BIOS/CMOS?

 

[Samstoned]

last time that happened to me it was bad cpu

how tight is that heatsink on there??
if you had spare ram would reset cmos/bios with that in it
power on power off then on again can be bad PSU
it's tough with new parts just where things go wrong

 

[Gradient]

I'm pretty sure it's the CPU, but I'm not sure what. The heatsink and fan seem to be firmly in place, with plenty of thermal paste. The fact I got an error message suggests that there's been a hiccup in the BIOS or CMOS, but resetting the CMOS has done nowt. I've no idea how to reset the BIOS, or flash it or whatever it is you do when the BIOS goes wrong.

 

[AlbertLionheart]

Given the symptoms of shorter cycles between restarts, this sounds heat related.
Take the CPU fan off and clean off almost all the gunk - the HTP needs to be spread really thin - too much is worse than none at all.

 

[Gradient]

I've reapplied the thermal paste, and repositioned the heatsink - just a retightening, but the restart cycle has stopped. It wasn't a persistant problem anyway, but I definitely had too much paste on. I checked the processor, but there didn't look to be anything physically wrong with it. I've tried clearing the CMOS again, leaving it without any form of charge for about an hour, but still nothing.

 

[AlbertLionheart]

A common problem with new builds is short circuits under the board - you need to be sure that you have no extra upstands under the board which could be shorting it out. Also check you have the front panel connections correct. If in doubt take the motherboard out of the case and see if it will boot with nothing other than the PSU and a speaker attached - start it by shorting out the pins for the power button; then add components one by one until you find the problem.

 

[Gradient]

I used the cardboard washers that came with the motherboard, but googling about I get the impression that I shouldn't use them; the motherboard is screwed in with 9 screws, six on the upstands on the case (on a seperate piece of metal, not on the side of the case itself) and three on the brass studs I screwed in myself. Should I remove the cardboard washers, then?

 

[Samstoned]

if to much paste has gotten down on the cpu board and or socket oops
that past is conductive could be a short there
silver is anyway
I like the little pad things no mess work every time
I used to make my own thermal paste
just to fussy a deal
I guess I started lucky being a cheap skate I used very little paste
I would even steal it from a office machine for a new scabbed build :blackeye:
:chef:

 

[Gradient]

Seems the restart problems are still there - it can stay on for a minute or so, then shuts down. Whenever it tries to start up again, it barely makes five seconds before shutting down again. The heatsink seems to be connected fine, but it barely gets any less cold than when the computer is off - even the heatsink on the graphics card gets warmer. Is it possible the heatsink isn't put in properly, and if so how would I go about checking? And would that prevent the computer from starting up entirely, even if it allows the computer to stay on for a whole minute?

 

[mailpup]

Maybe you have unstable voltage. Do you have another power supply to test with? Enermax is a decent brand but any brand can have a defective part show up.

 

[Gradient]

Unfortunately not; the only other PC components I have are in a laptop. I tried removing as many bits as I could, but it still didn't work. I think I'll take it to the repair shop I bought the heatsink from, because if it does turn out to be the heatsink at fault, I can probably wrangle a free replacement out of them.

If it turns out to be a more expensive piece of hardware like the CPU, I'll have to see if I can get a replacement unit from overclockers, which is where I bought everything from. If I can't, this PC is about to get a lot more expensive.

 

[Gradient]

Took it to a repair shop, who for the princely sum of ten British pounds declared the motherboard dead on arrival. I'm sending it back to overclockers, and buying a better board in its place (it was a cheap own-brand anyway). Thanks for the help guys.