MB or CPU fried, how to tell which?

Borgan · Joined: Jul 07, 2008 Posts: 3

First time here.. Hope somebody can help.

So my comp worked fine the other night. Then I went to use it the next morning after work, and all of the sudden I have no video output and It seems like its hanging somewhere.
I dont hear the HD grind so im assuming its not fully booting into windows. And it doesnt even initiate my monitor so i cant tell whats going on.

I tried reseating the card and no luck. I took my GF's card and put it in my comp and still nothing. I tried putting my card and my HD into her comp, and they both work.

I can only assume its the motherboard (most likely), the CPU, or ram, though i dont think bad ram would do this.
Any other possibilities?
And if its one of the 3 above, how do I determine which it is so i can replace it?

Thanks in advance, hope somebody can help.

clhenry · Posted: Mon Jul 07, 2008 5:19 pm Post subject:

My first question is, can you get in the bios?? or is that dead.

Borgan · Joined: Jul 07, 2008 Posts: 3

I cant get into anything. Theres no output to the monitor, even when I put my GF's card in.

clhenry · Posted: Mon Jul 07, 2008 6:44 pm Post subject:

I asked about the bios as on a number of ocassions, i checked computers that seemed dead, but i was able to get into the bios. Found that a glitch or virus?? changed a setting. By resetting the defaults they then booted up.
Did you pull the side off the computer and see if you have a couple red light on the mobo? They should be lit. Or change the battery? I know these seem like little things but it would be better changing a battery that a mobo or cpu.

drwho07 · Joined: Nov 29, 2007 Posts: 979 Location: Central FL, USA

At this early point, I'd have to say it's the AC to DC power supply.

They can be like light bulbs.....turn them on one day and poof they're gone.
Power Supply failure is quite common in Dell, Gateway and eMachine computers.

The give away is when the drives do not spin up and the fans do not start and the lights don't come on.

Then the LED's on the front panel work off of +5v, so no lights is another give-away the the power supply is GONE.

It's very seldom that a motherboard or CPU (almost never) just gives up the ghost on the spur of the moment.

If I were there, I'd connect your PSU to my PSU-tester and see if it has all its voltages. My first guess would be the -5v supply is gone. That's a very low current supply and very much subject to failure.

In the past ten years, I've never replaced a blown CPU chip, but I replace about a power supply a week.
If a motherboard does go bad, it's always a good idea to replace it along with a new CPU and ram.

Borgan, you may want to just take that PC to a service center for analysis and repair.

Good Luck,
The Doctor Cool

Borgan · Joined: Jul 07, 2008 Posts: 3

Alrighty. I powered it up again. All the fans appear to be working, including the fan on my vid card.
The CD rom light is on, but i dont hear it power up, and it wont eject.
I never hear the HD power up, or see the light for it on the front.
The comp stops responding after turning it on, the power button and reset button doesnt work. I have to hold power button for 10 sec to shut it off/reboot.

I built the comp btw, but not always the greatest at troubleshooting.
So, its the power supply, or something else?
And if it is the power supply, could it have damaged any other parts?

Oh, and I cant afford to take it to the shop. Those places are a rip-off, atleast around here.

Thanks again for the help. I do appreciate it.

BbWindowsHelpbB · Joined: Jul 07, 2008 Posts: 10

It's probably the power supply. I had this same problem on my dell. got a new one, and it works great!

drwho07 · Joined: Nov 29, 2007 Posts: 979 Location: Central FL, USA

It's unfortunate that everyone who wants to work on their own PC doesn't
have a little $14 power supply tester. You can have the +12 and the +5 and get some indications that the PSU is OK, but if the -5v line is dead, the PC won't boot up.

On a little eMachine I worked on a few months back, I tested the PSU when the PC would not boot up and sure enough, the -5v was missing.
I put in a new PSU thinking I had it fixed, but alas, the motherboard was bad too. My customer elected to give up on that PC and go buy a new Laptop. Rolling Eyes

Well, one tool that's invaluable around the home shop, is the Digital Volt Meter. I've seen them for as little as $6 at discount stores. I have two and I think I only paid $14.95 for the better one.

You can easily find the pin-out for the power plug, listing what voltage should be on what pin. That info usually comes with every new motherboard. Or you can look it up on the internet.

Good Luck!
The Doctor Cool

alphanumeric · Joined: Jun 02, 2004 Posts: 624

Did you try clearing the CMOS (resetting the BIOS) with the motherboard jumper. Talking the small battery out for say 5 to 10 minutes will do the same thing. I would try it before spending any money on new parts. If the battery has been in there for a while it may be weak and that can cause your BIOS settings to get messed up. Unfortunately unless you have another system to swap parts in and out of, diagnosing a problem like yours can be a pain. If it was me I would likely buy a new power supply. Of the three its likely the cheapest purchase and having a spare power supply if you guess wrong isn't so bad.