How can I debug my PC to isolate the motherboard?

[Zerohm]

So about 3 months ago I built a PC. Everything was working fine until suddenly it refused to boot. The mobo just beeped once and then I couldn't even get to a BIOS, no display at all. I pushed on all the cards, and it booted once, but since then I haven't been able to get it to boot at all.

I've tried clearing the CMOS, and now it seems to go through more checks, but I eventually just get the same beep and dead screen.

My question is what steps can I take to isolate the problem to the mobo? Won't motherboards boot into the CMOS even without RAM or a CPU?

-Zerohm

 

[Zap]

Originally posted by: Zerohm
Won't motherboards boot into the CMOS even without RAM or a CPU?

Absolutely NOT. Well, at least none of the boards I've used would. You need a working CPU, HSF, RAM, video, PSU, monitor and a keyboard to hit DEL (or whatever key combo).

General troubleshooting tips... remove everything from case, put motherboard on something that is non-conductive (I usually use the motherboard box and the foam sheet that is usually in the antistatic bag with the motherboard). Remove everything and then reinstall the CPU, HSF, RAM, video. Hook up the PSU, monitor and keyboard. Of course make sure everything is plugged in right. Hook up PC speaker (the little speaker in your case, unless mobo has one built in). Then, try turning it on by shorting out the power pins.

If it works, then start adding drives and expansion cards. If it still works, reinstall everything in case.

If it doesn't work, then you have to look and listen. Does the fans spin up like normal? Does the PC speaker make the normal single short beep? Does the keyboard lights flash and then NUMLOCK stay on (if it is set that way normally)? If you short out the power pins again, does it shut off? If all indications are that it booted up except you still get no picture, perhaps there's something wrong with monitor, monitor cable or video card output.

If it makes a rapid sequence of beeps, usually that indicates a dead or missing video card, or the slot has failed (this happened often BITD when AGP 8X first came out and AGP 2X cards shorted the slots out because of wrong voltage).

If it makes a long beep, much longer than usual, that often indicates RAM is missing, failed, or a bad RAM slot.

If it powers on but no beeps at all, try removing video card and power it on, then try removing RAM and powering it on. This is to try "forcing" it to beep an error - which will usually mean the CPU and motherboard is okay.

If you can get it to beep at all and the keyboard lights don't flash, perhaps a dead motherboard, CPU or PSU.

If it won't turn on at all (fans on CPU and in PSU don't spin) then it often is dead motherboard or PSU.

Let us know what you find out.

 

[Zerohm]

Thanks, Zap for the time and effort you put into that response.

All fans are spinning, optical mouse is powered, but I only see lights on the keyboard when I hold the power switch to power down. I removed all parts, and replaced only essential parts. I get the same beep. It does sound like many beeps in succession, but I'm not sure.

Remove the video card only - the same beep occurs, but it seems like it could be quicker from time of power on.
Remove the RAM only - normal period of checks, but completely different error code and beeps continue indefinitely (seems much different)

I'm really starting to think it's either the videocard, or the videocard slot. It's a PCIe XFX Geforce 6600gt, and I'm going to give it to a friend to test as I don't have another PCIe board lying around.

Thanks again.

 

[Zap]

Yes, sounds like video card or slot. The video beep is usually a sequence of four, very rapid beeps with the last one a hair longer than the first three in a staccatto "be-be-be-beep" that takes only about a second or two. The other indefinate beep is definately RAM - is it just a longer "beeeeeeep" that keeps repeating? At this point, until we have more information I'd say video card or slot.

Also, forgot to mention... have you tried clearing BIOS?

 

[Zerohm]

Yeah, the BIOS is cleared by clearing the CMOS right? Well, before I cleared the CMOS, the motherboard would beep very quickly. After clearing the CMOS it seems to go through a more extensive series of checks before the beep. When the beep occurs, the error display reads 26, which is "Reserved" in the manual. However, except for when I pulled the RAM, the error display will go through a few more numbers and land on 7F, which is

"Switch back to text mode if full screen logo is supported
-If errors occur, report errors & wait for keys
-If no errors occur or F1 key is pressed to continue
*Clear EPA or customization logo"

Again, this seems like a video issue.

And yes, your description of the 4 rapid beeps does seem like what I'm getting.

P.S. I forgot to mention when I pull the CPU, I get no beeps, the mobo just sits there displaying "FF", which is just listed as "boot attempt".

 

[Zap]

Yeah, no CPU = no POST, guaranteed. You have a POST code on your mobo? Epox?

Have you gotten your friend to test your vidcard yet?

 

[Zerohm]

Yes, Epox board.

Still waiting on my friend to test, I can't really bug him because after all he's using his time to save me the $50 the local PC shop wants for a diagnostic .

 

[Zerohm]

well my video card worked on another baord, so I sent the mobo back, got a new one and everything works fine.

I just hope I don't have some screwy voltage mismatch that causes the mobo to burn out every 3 months or something like that.

 

[Fern]

Seems unlikley to me, but you never know.

Might check the PSU's voltage rails. Look in BIOS or use a multimeter.

Good Luck with the new mobo.

Fern