PC failing to post - help with diagnosis

Zaphan58 · 17 Jan 2009 at 12:57

My PC was fine then all of a sudden it has started to not even post.

I switch it on it powers up but nothing else no beeps, nothing. Some of the time it powers up (I'm posting on it now) but the CPU gets set to about half it's speed in the BIOS. I find if I clear the BIOS it tends to boot up fine no problems but again the CPU is set very low. It gbooted the other day and I got into windows but it shut down because it was beeping that it was overheating.

Also there's some crazy voltages being read in the BIOS the -12v rail is reading like -60v and the +5v rail reads +4v some of the time and then sometimes flicks back to a steady +5v :confused:

I'm thinking either the power supply (Seasonic 430W) has had it or the motherboard (Abit NF7-S)

Here's a pic of the voltages. Edit: If you look at the +5v rail the reading looks rather garbled too.

ThundyCat · 17 Jan 2009 at 13:05

I'm no expert but sounds like the PSU is on its way out?

Deadude · 17 Jan 2009 at 13:18

what temp is ur cpu running at??

ChrisLX200 · 17 Jan 2009 at 13:46

Does it do this at stock speeds/voltages?

Zaphan58 · 17 Jan 2009 at 13:57

Deadude said:
what temp is ur cpu running at??

No too sure in the BIOS it was running at about 40c after a few attempts at booting. This is with the XP-2500 chip running at 1GHz I can't get it to boot set at much more. I will install a program so I can check the temp in wondows.

ChrisLX200 said:
Does it do this at stock speeds/voltages?

Stock speeds and voltages it fails to even post.

Zaphan58 · 19 Jan 2009 at 18:47

Right guys I just tried a different PSU. Once I manage to get into BIOS the voltages look a lot more normal but I am still having problems to even get it to POST still. It just kind of powers up but the screen stays blank until I clear the CMOS then it sometimes boots. I'm not sure wether the PSU being a 300W I just tried as opposed to the 430W I was using has anything to do with it though.

I'm thinking the PSU may have blown it's load and taken the motherboard with it? Sound likely?

linktoinsanity · 19 Jan 2009 at 19:03

Try a more powerful PSU, other then that, sounds like your motherboard mate. I can't think of anything else it could be. It's not your video card isit? (Note: Stab in the dark)

ChrisLX200 · 19 Jan 2009 at 19:07

If you've been using heroic overclocks/overvolts I'd guess the CPU was fubar, otherwise (CPUs being tough if treated right) I'd go with the motherboard being at fault.

Zaphan58 · 19 Jan 2009 at 19:17

Mattf121 said:
Try a more powerful PSU, other then that, sounds like your motherboard mate. I can't think of anything else it could be. It's not your video card isit? (Note: Stab in the dark)

I will try a different PSU if I can find one. I do have another graphics card laying round so I will give that a go.

ChrisLX200 said:
If you've been using heroic overclocks/overvolts I'd guess the CPU was fubar, otherwise (CPUs being tough if treated right) I'd go with the motherboard being at fault.

I used to run overclocked but I've been running at stock for over a year now. Does sound like the motherboard has gone, I find it odd that I still get the same problem yet more normal voltages in BIOS with another PSU which is why I thought both may have gone.

Zaphan58 · 19 Jan 2009 at 20:30

Righty it finally booted again and I'm posting on it now. I switched the PSU yet again for a Tagan 480W and I still get the same problem. When it booted this time it said the CPU was unworkable so I fiddled in BIOS again and saved the settings after it saved It just black screened again and failed to boot. After about 10 attempts to boot it finally did with the CPU detected properly and I'm posting now. I guess the motherboard has had it. Question is was the PSU the murderer or is it ok.