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no POST (sometimes) - can it be a psu issue?

K

Karissa

n00b
Joined
Aug 5, 2005
Messages
9
Hi, it's my first pc build and it's not looking good.

If the machine is cold when I power it on, it will POST ok. However, after running it for a little while and powering it down, I cannot turn it back on again. There would be no post (monitor on standby), no light flashing at the keyboard, it just keeps running and fan spinning. If I turn it off again, unplug power and plug it back in, the fan would kick up spinning loud, still no post and no lights to the keyboard.

I have tried with minimum config (mobo + cpu + 1 stick of ram + video) but it's the same result. Sometimes it will POST, sometimes it doesn't. The only way it guarantees to work so far is if I let it sit idle with power off for 30min and try again, then it normally POST fine. Once it post, it can run fine for several hours (i haven't tried longer time).

I've tried resetting CMOS, changing bios chip, RMA'ed mobo, using 1 stick of RAM only on different slots. Video and HD work when tried on another computer. So the only parts I can think of are cpu and power supply. Am I missing something? It's my first build too so I hope I haven't connect anything wrong to cause this. Does it sound like a psu problem to you?

Rebooting is ok so I would restart into bios to check the temperature before shutting it down. Just making sure it's not overheating. The cpu temp is around mid 40s celsius when I shut down. I check the temp whenever it POST successfully too. The highest temp I recall is 41 (when it POST successfully). It has never shutdown by itself or give BSOD.

Any ideas? Thanks. :confused:
 
voltages from bios as follow:


CPU 1.39V
AGP 1.47V
3.3V 3.24V (sometimes 3.26V)
+5V 4.89V (sometimes 4.91V)
+12V 12.03V
-12V (-)12.19V (at startup)
(-)12.28V (after running for a while)

RAM 2.59V
5V SBVIN 4.94V
voltage battery 3.05V
 
Get a digital multimeter to get accurate readings, but i think its more a motherboard issue than a psu one.

oldmx
 
^^Agreed to be sure its accurate you gotta use a multimeter. The fact that you say after letting it sits makes me believes its a cap issue somewhere. Like the cap isn't holding charge properly. Could be the PSU or the mobo, altho the fact that you RA'd a board. I would try a replacement supply before you did anything else. Because I have seen a slew of PSUs from one manu that checked fine on the meter, but once I replaced it all the issues went away.

 
Yeah I thought mobo was it too until I received the RMA and it gives the same symptoms. I can likely get a hold of a 350W psu (although it's a pain).. I'm pretty newb at this, I hope it is compartible with my system. Not sure where to get multimeter either!
 
Karissa said:
Yeah I thought mobo was it too until I received the RMA and it gives the same symptoms. I can likely get a hold of a 350W psu (although it's a pain).. I'm pretty newb at this, I hope it is compartible with my system. Not sure where to get multimeter either!
Click to expand...

Take the board out of the case and run it for a while like on a table

and list the system components while you are at it.
 
It might very well be the powersupply. It's funny how the powersuplly is the last thing that people tend to think of when they run into problems with the computer.
 
What kind of board do you have? I've had a continuing problem with cold boots and DFI boards. Guess I'm a glutton for punishment because I keep buying them.
 
Ok I dug up a 350W psu just to found out it's lacking the 4-pin connector to the motherboard. Can I still try it or will it mess up my motherboard? I'll do some more searches but please help a newbie!
(Edit: 20pin psu -> 24pin mobo Oh no, i guess it doesn't work .. :( Is it true it'll whack the board?)

Google says DFI = 939 nForce 3 agp board so I guess that sounds right. I have a shuttle mobo, NVIDIA nForce 3 250GB chipset. What is your problem with cold boots, texuspete00?
 
It won't whack the board, but it probably wont post either.
 
Thank you for the replies.
Yes I have tried holding onto the power button with power cord detached, but no change.
 
Ok.. We need to get this out there....

What kind of motherboard and what kind of PSU?

Thanks!
 
Thank you for the replies.

It's a shuttle system,
motherboard: FN95V3.1 (NVIDIA nForce 3 250GB chipset)
psu: shuttle silent x 240W

I just had my first no POST where time (waited 40min) did not fix it. I had the computer running for over 6 hours before turning it off and switching it on again and got no POST. I'm very puzzled now, did it just die? I contacted a Shuttle engineer and we're trying to RMA the mobo again, maybe I should RMA the psu too? or do you think it's the cpu?

:: confused ::
 
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