Usually tells me the motherboard is drawing too much power due to a short or other issue.
I usually start by moving the motherboard, CPU and HSF to cardboard leaving all other parts out for a power up test on cardboard with the PSU. If this works I check the case for extra mounting posts that over time can wear through paint on the motherboard and short out.
If it still won't power up then I unplug the CPU and go for a power up test. If that fails it's the motherboard or the PSU (rarely!)
The thing is that at this point you need spares to figure out which part it is.
Need some advice. I have a server that for a few weeks had been crashing - reason unknown. I'd find it in a sleep state but with fans running. Power off button would not work even holding it down for a long time, had to unplug from mains. Anyway, went away on holidays having shut to down properly.
Returned home after two weeks and tried powering on - nothing. Opened it up and could see led on on the motherboard when PSU switched on but power on switch did nothing. There was no sound from the PSU. I then did the following tests & checks :
1. Replaced the power on switch and cable with one I had lying around - did not solve the problem.
2. Removed and replaced the CMOS battery - did not solve the problem.
3. Removed all PSU cables from motherboard and other devices, did the "paperclip" test and I could here sound from the PSU and the PSU fan would spin. I further tested the voltages on all motherboard pins (24pin connector and EPS 12V 8 pin connector). All of these were reading correct voltages.
4. I then found (by chance) that if I only plugged in the motherboard 24 pin connector and left the 8 pin EPS 12V connector unplugged, the power light on the on/off switch (plus another led on the motherboard) would flash on/off about every second and the CPU fan with part spin with evety flash. When I connected the multimeter to the unconnected EPS 12V connector, I could see the voltage was surging to 12 volts in unison with the led flashes - then dropping and surging again.
I suspect my PSU is the culprit - it can hit the required voltage when there is no load but cannot maintain the voltage. Hence the surge on/off and leds and CPU fan on/off. However, I suppose it could also be the motherboard or CPU.
As I don't have any spare parts, anything I do is going to cost money, so if anyone can advise where I should start? Am I right to have a go with PSU first?
I using an Intel Motherboard, ATX form, and an i7 CPU. The server has been running for about 4 or 5 years and does very little (i.e. understressed) - just file serving and controlling household backup process for some laptops. It also serves has a household music and ebook server.
Thanks (this is my first post here)..... Alan
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