View Full Version : This sound like a power / PSU prob?

Speedy Gonzales
06-07-2009, 12:01 PM
The other PC here (if you pull the plug out, say if youre wanted to move it), refuses to turn on sometimes. It'll turn on, the power LED lights up, BUT nothing else happens (you cant hear the hdd doing anything, and the hdd LED doesnt come on).

In order to fix it, I have to remove the CMOS jumper then put it back to fix it, then reconfigure the settings in the BIOS. BUT, its fine, if you shut it down, then turn it back on later / the next day.

I'm not too sure if the prob is the Restore on AC power loss option in the BIOS (or something similar, which is on Power OFF). BUT, the option for this PC is also OFF/Disabled. And its fine. The latest BIOS is on it. I cant think of anything else that would cause it not to boot (if you unplug the power). Anyone have any ideas on what maybe the cause and how to fix it permanently??

06-07-2009, 12:44 PM
I once had a PC with a similar problem - the issue turned out to be a faulty thermal protection circuit. Is it reporting anything unusual with the temps?

You say it has the latest BIOS version - does this mean you've flashed it, or that it already had the latest version?

Does Google turn up any results for similar issues by other users with the same motherboard?

If you unplug the data cable for the HDD, but leave the power connected, does it spin up when the system is in this state? If not, that would indicate a problem with at least one of the 12v rails on the PSU.

By "nothing else happens", I assume you mean no POST? Is the system speaker disabled, or are you simply not getting any beepcodes? Does the system have a facility to output early POST feedback via the LEDs (many Dell systems have this ability).

Speedy Gonzales
06-07-2009, 12:54 PM
It didnt come with the latest BIOS on it, but the latest BIOS has been on it for at least 2-3 yrs till this prob popped up recently. Didnt really notice this prob before, because the PC has never been moved (from where it is now)

There is no post (there is a speaker in the case), but it doesnt beep (after I pull the plug that is, it does post / and beep normally).

BUT the power LED is on. No nothing else to tell me WHY it wont post. I'll check the temps later (in the BIOS), no programs are installed to tell me the temps etc. But I'm pretty sure the temps are fine. or I doubt it would stay on for 12 hrs + a day. I'll have to check about other users having the same prob. Its an Asrock (478 pin). So probably not :p It was the only mobo available then (when the old ASUS 478 pin mobo died), that I could find. I dont think the PSU is the prob, it uses the same PSU as the PC in the bedroom, I swapped them still the same (and the PSU in the bedroom is fine). I thought the videocard could be the cause as well. BUT, no it did the same thing. I'll test the hdd cable later as well, the flatmate uses it (shes on it atm).

06-07-2009, 01:26 PM
I have a Samsung 17" LCD here that does something similar.
If you leave it plugged in to the power you can turn it on and off 'till the cows come home.
As soon as you turn off the power at the wall or unplug the power and plug it back in it won't turn on.
You have to leave it plugged in to the power for a couple of hours first then it will turn on again.

06-07-2009, 01:40 PM

06-07-2009, 01:43 PM

That would be my suspicion too - either that or the CPU, but realistically CPUs don't fail anything like as often as motherboards do.

06-07-2009, 01:46 PM
Grab another psu and test it...

Speedy Gonzales
06-07-2009, 01:57 PM
Grab another psu and test it...

I did it made no diff, if the prob was the CPU, wouldnt it do something like crash often or something if it was faulty? It doesnt

06-07-2009, 02:02 PM
Sounds similar to one i have at home but sometimes it wont post or boot for ages even if i unplug it them plug it back in. Have changed CPU and power supply (another similar but still old) and updated bios.
I would say mine is MB too like yours

06-07-2009, 02:09 PM
Ok lets make a list then.


Now start eliminating them.

Speedy Gonzales
06-07-2009, 02:12 PM
Well I doubt if its the ram it doesnt crash, it can stay on for 12 hrs + without crashing. Likewise for the hdd. Or the video. Everything is fine and works fine, once its up and running. Its only when you unplug it, it doesnt want to post. May have to find another (if I can find another socket 478). Or update it completely. Just replace the mobo, cpu, video (if its not onboard, its only used to get on the net and for playing cards online, so doesnt matter whether the card is onboard or separate), and ram. And keep the monitor, hdd's, (altho I may replace the hdd, as its only SATA 1), and case (altho I may replace this too), and keyboard/mouse.

06-07-2009, 02:17 PM
That leaves Mobo and CPU.

Definetly Mobo.

Speedy Gonzales
06-07-2009, 02:22 PM
Well if the mobo is the prob, anyone have a new socket 478 mobo :p Other than that, I'll have to buy parts bit by bit, then put it together.

06-07-2009, 07:49 PM
Have you tried new BIOS battery?

Flat battery often produces interesting results...

Speedy Gonzales
06-07-2009, 08:01 PM
The battery wont be flat, its maybe a yr - 2 yrs old.

06-07-2009, 09:05 PM
How do you know how old it is?

Does it have a datecode on it?

Speedy Gonzales
06-07-2009, 09:14 PM
Because I know when I brought it down the road, its not the original battery

07-07-2009, 01:46 AM
Not sure what is happening here but I suspect a flat CMOS battery as well.

In the event you want another motherboard 478 I do have a source but I ain't going to phone him right this minute.

07-07-2009, 01:49 AM
I would still check the battery just in case