PC won't boot, fans only spin briefly, PSU good

[flyck]

Hello,

Any help on this will be greatly appreciated.
I have 8 year (!) old system that worked perfectly fine, until now.
Asus a8n sli deluxe, Athlon 3800+ x2, 2x1G + 2x512M DDR.
Two days ago I unplugged from power and left it like this for some 36hrs. When I tried to boot again, I got this problem:
Motherboard green led is on, when I push the power button, CPU and case fan spin briefly (for less than one second) and then stop, nothing powers up. If I power cycle the PSU, and push power button again, the same brief spin happens.
Ruled out bad PSU - works fine on another system.
Unplugged everything, left only CPU (and heat sink+fan), one stick of memory (tried all the sticks) and graphics card. I don't even hear bios beeps.
I see no visible damage to capacitors around.
Changed the battery and reset RTC ram too.
Since I don't even hear BIOS error beeps, I guess something in the power circuitry of the mother board is wrong. I have simple multimeter - is there something I can measure in order to find out what went wrong?
Any ideas how to troubleshoot?
I understand the PC is pretty old and I can afford new one, but I have sentiments on this system and besides If I can fix it I prefer to do so in order to avoid environmental pollution.
Thanks

flyck

 

[stickg1]

Do you have a speaker attached to the internal speaker header?

Did you try clearing the CMOS?

 

[flyck]

Thanks stickg1,

Yes, I have small speaker attached, I remember once it worked, I'll have to verify it is not faulty.
I used a jumper to clear CMOS as per instructions in motherboard manual.
Also changed the battery.

 

[satyamdubey]

remove the graphic card as well and then try booting up. also you can try powering up without RAM and you might get a constant beep. Thing is, right now it seems your system is not even POST'ing.
If the ram beep thing happens that means that POST is initiating and probably we all can narrow down to the fault.
good luck
- satyam

 

[flyck]

Thanks satyam,

Actually I didn't know that it is possible to POST without RAM/graphics card. Well, I removed them both and I have exact same behavior.

Now when I think of it, the fans should spin independently of POST, am I right?

Thanks,
flyck

 

[squerldestroyer26]

It depends on where you have them plugged into. If they are plugged into the motherboard headers, then they are controlled by the bios. If they are plugged directly into the power connectors on the PSU, then they will run regardless if the bios boots or not. It sounds to me that you have a motherbord that is bad, especially since you removed the graphics card and got the same result.

 

[juiceman]

Are you sure you have the aux CPU power cable connected?

 

[satyamdubey]

I think your thermal paste has died causing the processor to overheat and shut down. you should try cleaning out the old compound and reapplying a good quality one like arctic silver. refer:
http://www.tomshardware.com/forum/324993-28-cleaning-thermal-compound
I think this might work for you
good luck

 

[flyck]

It depends on where you have them plugged into. If they are plugged into the motherboard headers, then they are controlled by the bios. If they are plugged directly into the power connectors on the PSU, then they will run regardless if the bios boots or not. It sounds to me that you have a motherbord that is bad, especially since you removed the graphics card and got the same result.

Thanks squerldestroyer26
Fans are connected to the motherboard headers. I agree it's perhaps motherboard fault

Are you sure you have the aux CPU power cable connected?

Thanks juiceman,
Yep, double-checked this, also with another PSU

I think your thermal paste has died causing the processor to overheat and shut down. you should try cleaning out the old compound and reapplying a good quality one like arctic silver. refer:
http://www.tomshardware.com/forum/324993-28-cleaning-thermal-compound
I think this might work for you
good luck

Thanks satyamdubey,

I can try this, though I am skeptic - I think it takes more than half a second for CPU to overheat and shut down.

 

[bemused_fred]

You think this is the motherboard's fault? I think I had a similar situation with the old P.C. I was assembling. Are your standoffs connected properly? Is there any way the motherboard could be improperly connected.

 

[satyamdubey]

I agree with you that it seems unlikely that a cpu would heat up to critical temp in less than a second (and squerldestroyer26 may be right in suggesting a dead mobo as the problem) but there are three interesting links that I'd like to share:
1: http://uk.answers.yahoo.com/question/index?qid=20110128112447AAv5V1O
2: http://forums.anandtech.com/showthread.php?t=2216761
3: http://www.scribd.com/doc/7262946/CPU-Maximum-Operating-Temps
there is a chance that cpu can heat up in seconds and AMD 3800+ has 64 C as its critical temp and AMD has lower temp limits set for its cpu's compared to Intel (that second link has awesome stuff written by a senior poster by the name "IDontCare")

CPU's have a critical overheat protection that is always enabled and cannot be software controlled all this achieved through a temperature sensitive diode. Since AMD sets a lower limit to critical CPU temps and CPU's can reach that temp within a second, it is possible that overheat protection might be turning off your system

 

[flyck]

I agree with you that it seems unlikely that a cpu would heat up to critical temp in less than a second (and squerldestroyer26 may be right in suggesting a dead mobo as the problem) but there are three interesting links that I'd like to share:
1: http://uk.answers.yahoo.com/question/index?qid=20110128112447AAv5V1O
2: http://forums.anandtech.com/showthread.php?t=2216761
3: http://www.scribd.com/doc/7262946/CPU-Maximum-Operating-Temps
there is a chance that cpu can heat up in seconds and AMD 3800+ has 64 C as its critical temp and AMD has lower temp limits set for its cpu's compared to Intel (that second link has awesome stuff written by a senior poster by the name "IDontCare")

CPU's have a critical overheat protection that is always enabled and cannot be software controlled all this achieved through a temperature sensitive diode. Since AMD sets a lower limit to critical CPU temps and CPU's can reach that temp within a second, it is possible that overheat protection might be turning off your system

Thanks satyamdubey,

Indeed very interesting links - very comprehensive explanations. I will try to dismount the CPU and heat sink, apply fresh thermal compound and re-mount. I have old working Athlon 3000 too, I'll try with it too.

You think this is the motherboard's fault? I think I had a similar situation with the old P.C. I was assembling. Are your standoffs connected properly? Is there any way the motherboard could be improperly connected.

Thanks bemused_fred,

Well, this system is running stable for years - nothing has changed mechanically. Anyways, I am going to disassemble it from the case and assemble again

 

[daman05]

Hey there, any updates? I seem to be having the same problem with the same mobo and X2 4800+

Took the same steps as you (apart from taking apart CPU) and still no results. PC has been running almost non-stop for ~8-10 years and one day its off and I have this problem.

Used it as a server for a long time and don't want to have to move all my HDDs to a new PC!

 

[JasonRage]

I had a very similar problem. Put the PSU on a tester and it read as it should. It was still the problem though. Sent it in for RMA and the replacement worked perfectly. Try another PSU.