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CPU or Motherboard dead, help!

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November 10, 2010 10:28:41 PM

Hi guys, sorry if i posted in the wrong section but there isn't a "General Help" section that i can find, so i'll post it here.

Ok so my 8 year old PC is acting up weird and not working properly. Everytime i turn it on, i get no screen displays at all, shows no information at all, not even the pre-bios information (the stuff you see straight after turning on your PC, such as the BIOS information, whether your hardrive status are OK etc).

Normally, straight after turning the PC on, the system will beep once and then show all the screen information. But mine doesn't do that anymore.

I unplugged everything and checked that they're all ok, plugged them back in and still couldn't get it to work. Sometimes it works, but very rarely.

There's nothing wrong with my ram or monitor or graphics card, they all work fine. I'm thinking maybe it's the CPU or motherboard coz they're quite old already. I'm using a ASUS P5GD1 motherboard, and a Pentium 4 3.4GHZ Northwood CPU.

I'm not sure whether it's the motherboard that's died or the CPU, I can't really tell and i did a lot of Google search on this and there doesn't seem to be a way to tell??

All i know is, all the fans work, so nothing is really dead......


Oh and i also replaced the CMOS battery with a new one but still it doesn't work.

More about : cpu motherboard dead

November 11, 2010 12:01:16 AM

probably the mobo, most capacitor couldn't last that long (8 years O.o), except if the caps are solid one.... also check the PSU... PSU's also have a predetermined lifetime, since it contains plenty of capacitors. if you use the PC very often (nearly 24/7) dont expect the PSU to lasts for 3 years

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November 11, 2010 12:44:04 AM

thanks for ur reply!

Ok first off i can confirm it's not the CPU's problem. It was able to produce the error beeps so that shows it's working.

If you guys refer to here (or Google):
http://www.pchell.com/hardware/beepcodes.shtml

It shows that the short beep is normal for every BIOS. However, I get no beeps so it's either the motherboard or PSU like you said.

So what I did was use another PSU from my other working PC and connected everything and turned back on, but still doesn't work. So i'm pretty sure it's not the PSU's problem.

But, I also think it *could* be the ram, because sometimes it'll beep 3 times, which shows that it's the memory's problem.

I haven't got another motherboard that takes DDR ram so i can't do a MemTest on the rams, but what I did was test each of my ram sticks individually (I have 3), and I either get no beeps or 3 short beeps. So maybe this could really be the motherboard??
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a c 172 à CPUs
a c 156 V Motherboard
November 11, 2010 12:50:05 AM

Work through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.

I have tested the following beeps patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:
http://www.cwc-group.com/casp.html

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

Motherboard LED's mean very little. When on, all they are telling you is that the computer os plugged into a live power socket and the PSU is switched.

Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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a b à CPUs
a b V Motherboard
November 11, 2010 1:03:04 AM

On a computer this old the first suspect has to be a faulty power supply. This is also the easiest and cheapest part to fix. Substitution is the best test for a faulty power supply. The processor is ok as it would not beep if the processor was faulty. The computer would probably be not be worth fixing if the motherboard was faulty.
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November 11, 2010 1:06:56 AM

Quote:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.


ok it looks like it really is the memory's problem, however i'm not sure if it's the ram sticks themselves, or the motherboard's ram slots. I tested just then without the graphics card plugged connected to the power supply, it produce a single long beep, i let it beep for about 15s until turning it off. After plugging power to the graphics card, it doesn't do that anymore. So then i tested the ram by taking all the ram sticks out, it produced 3 short beeps which indicates memory problems. I then put them back in and now i get no beeps at all, just like before. However, sometimes the system will produce 2 or 3 short beeps with the ram still in it, which indicates memory problem as well.

So now the problem is, i need to somehow find a motherboard that supports DDR ram so i can do a memtest on them, either that or it's the motherboard's problem coz of the ram slots??


And also, so as long as i can hear beeps, it's not the PSU's problem then?? If so, that's great, and as i've mentioned in my previous post, i used another PSU (CoolerMaster 650W, working no problem) and tested it, and still nothing shows up, so it's not the PSU's i'm pretty sure.

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