Dead Motherboard?

[LuckyTxGuy]

Ok, time for me to ask a question.

I've got a customer/friend's E-machine desktop here and it's a freebie job so I don't want to spend forever fixing it. The friend is older and knows little about computers. They said one evening when they booted it the keyboard wouldn't work and everything seemed really really sluggish. Then the mouse wouldn't work, but they got XP shutdown. (pulled the plug?) Anyway, next day it's dead. Nada. Won't power on at all.

Enter: Me. I bring it to my office plug in a power cord and hear a quiet but high pitched squeal from the PSU and the machine is dead. No lights, no fans, NOTHING. I assume it's a bad PSU. My PSU tester shows that the PSU is putting out too much power, it doesn't give me an exact reading but the code translates to too much power. I put in a brand new working PSU thinking that is it and to my surprise, nothing. Dead.

Then I'm thinking it's the power switch. I used my meter to determine the switch is in fact working. Odd. This thing is just flat dead.

Any thoughts? I've almost convinced myself it has to be the motherboard. What do ya'll think?

[buckslayer80]

Hmmmmmmmmm.

Well if we think about the order of a PC's power up cycle in order, you solved the first 2 stages. Do the fans or anything come on now? Even with a dead MB the primary fan on the PS should still spin if its getting power, right? Everything that's directly connected to the PS should power on if its not dead.

Do you have an Experts Exchange account? Being in the biz it's the best $25 you'll ever spend. I'll post it on there for you. They usually respond pretty fast. I'll post what the big boys have to say.

[SamIAm]

If the motherboard dies, it can take other stuff with it, right? When my PSU died, it emitted a high-pitched squeal, and took the motherboard along for the ride.

[ QUOTE ]
Everything that's directly connected to the PS should power on if its not dead.

[/ QUOTE ]
Keep in mind that the PSU doesn't send power to the fans all the time, but only when the rest of the computer's on. Since only the motherboard knows whether the computer's set to "on", but the PSU gets power from the wall all the time, the PSU must listen for the mobo to know whether to send juice to the fans. This means there are dead motherboards that cause the PSU to not activate the fans.

Am I off base here? I'm making this up as I go along.
-Sam

[LuckyTxGuy]

Thanks for the replies guys.

Buck, I thought EE was about $100 a year? Either way, I need to join up I've just been too lazy. Their site is always the first search result when I google error messages and such. Glad to hear it's worth it, I'll look into it.

When I say this thing is dead....I mean dead. With the new PSU still installed and the power cord plugged in, absolutely nothing at all happens. I'm talking nothing. Nothing spins, no lights, nada. However......when I plug in my digital PSU tester, the PSU fan starts to run very quietly as the PSU powers up. So this leads me to believe the PSU doesn't even know it's plugged into the motherboard, ie: the mobo is dead. (?)

Sam what you are saying about powering up fans etc, makes sense to me too. Whether it's right or not, I don't know. [img]/images/graemlins/smile.gif[/img] Sure sounds good though.lol

I can't stress enough that even with the new PSU installed, everything (including the PSU) acts dead as a door nail, until I plug in my PSU tester and then the PSU comes to life.

What I wondered was if the high voltage that my tester is showing on the old PSU didn't take out the motherboard and who knows what else?

Thanks for the help. The problem is if this thing is toast, and it's not worth spending much $$ on, it's going to be hard to explain to these (older) folks that their computer just "died".

[DQPaulie]

Some eMachines had PSUs that would kill the motherboards ( google it ). Happen to my friend, had to buy an overpriced motherboard from emachines, which they supplied a PSU with for free. They would make you call before placing the order, and they told you to make sure you did not use the original PSU. I went through them for this motherboard because it was oem windows, and I wasn't sure I could reinstall without the same motherboard at the time.

Paulie

[buckslayer80]

"Some eMachines had PSUs that would kill the motherboards"

Well this is what they think too. I'll post their responses. Beat: eMachines

Unfortunately, a bad PSU can damage whatever is connected to it, so now you have a possible dead motherboard or hard drives or video card (if it was plugged into the power supply). E-machines is not exactly the brand that comes to mind when thinking of reliable hardware, either.

So we definitely have a bad psu and it looks like it took out the motherboard, its very likely other hardware was also damaged. I have seen bad power supplies especially ones with over voltage issues take out multiple pieces of hardware(cpu, video card, hard drive, etc). Is the system still under warranty? If not you could replace the motherboard but there is a good chance other hardware was fried. For a much as it may end up costing in the end they may just want to get a new system.

what do you mean? too high voltage? that can and will damage the connected components.
i would start by testing all components on a good working PC first : new PSU, disk, ram, cd drive, PCI and video cards, etc . . even CPU if possible.
then start with the good devices, with a minimum :
mobo+cpu+1 ram stick, video card and PSU --> any display?if not : one of the connected is bad; try swapping ram, video card, psu

ps - if you want to test the old PSU, use a V-meter to check the outputs first; look here for how to :
http://www.fonerbooks.com/power.htm
http://www.duxcw.com/faq/ps/ps4.htm

Ouch - sounds like a dead mainboard too. Did you notice any cap leakage or physically blown capacitors around the ATX connector or CPU socket? I have experienced many faulty PSU's and generally I notice a physical sign with regard to too much juice being pumped out of the unit. Either as I mentioned, blown or leaking capacitors or if it goes further than mainboard - check the IC's on the HDD board etc.

Out of interest - does the new PSU that you fitted work on another board? When you checked the power switch (assuming you meant from mainboard header not PSU rocker) - did you disconnect and manually 'jump' the pins?

[LuckyTxGuy]

I'm tied up today but I'll post back this evening. Thanks for the info fellas.

I will add that this E-machine is several years old by no means worth spending more than $50-$100 max on. If it were mine, I wouldn't spend that much.

[buckslayer80]

[ QUOTE ]
I'm tied up today but I'll post back this evening. Thanks for the info fellas.

I will add that this E-machine is several years old by no means worth spending more than $50-$100 max on. If it were mine, I wouldn't spend that much.

[/ QUOTE ]

If you get time still try and figure it out. It would be good for guys like me and you in the future when we're making repairs.

But my guess is the problems is bc eMachines are pieces of crap. I don't know if you guys relaized but they used to give them away free when you signed up with certain ISP's. So they're obviously going to put together the cheapest POS they can from whatever parts are the cheapest. And apparently this included the world's worst power supplies.

[LuckyTxGuy]

Ok, I've got a few minutes.....

Totally agree that I need to figure this all out, just for experience sake. However, being a freebie job I can't spend a week on it, especially since the computer isn't worth $100 because it's so old.

E-Machines PSU kills motherboards = bad.lol Honestly that would explain everything.

My PSU tester is this one right here.... Newegg link It seems to work well every time I've used it. Basically, when the voltage is too high or too low coming out of the PSU it gives you a code that indicates whether it's too high or a code that it's too low, or if it's in the proper range it gives the actual voltage. Every time it shows the code that the voltage is too high. Not good. Then I plugged in the molex power connector that had been going to the CD drive and my tester showed the voltage fluctuating very badly. So that confirms my suspicions of the bad PSU. The new PSU has not been plugged into another working pc, but the PSU tester shows all the voltages to dead on perfect and in working order. AND for the record, I plugged in another working PSU into the E-machine motherboard and the results were the same. Dead. Oh BTW, I did short across the pins on the mobo, bypassing the on/off switch, to see if the pc would come to life and nothing happened. Still dead.

I'm agreeing with everyone else so far. The PSU crapped out, which now seems to be a known problem, it took out the motherboard and who knows what else. The video/sound are both integrated so the only external component (besides the drives) is a PCI 56k modem.

I can get my hands on an old motherboard at my office on Monday and try to hook up the PSU, drives and 56k modem, just to prove they are working, but I honestly don't think that matters at this point. I can't advise these people to spend any money on a computer this old. If the PSU had fixed it....that would be one thing for $30, but a PSU, motherboard, maybe the processor.....not worth it.

The one thing I did want to be sure of is that the motherboard was dead, which is seems pretty obvious it must be. I just didn't want to go tell this folks their pc was dead and be giving them bad info. Again, we're dealing with people over 65 here so their knowledge and understanding of this is very very little. They'll trust what I say, but I'm going to have to explain it to them in a way they'll understand. I think ya'll know how older people often are...they don't like to throw things away.lol

Thanks for all the help fellas. If someone thinks of something, pass it on, I'm still listening.

[buckslayer80]

Beat: "the only external component (besides the drives) is a PCI 56k modem."

That PC ain't worth $40.

And here's how you explain it to them: "You see this part here? It went bad and shot tons of electricity out to all these pieces here. Way too much. So now nothing works. Comprende?"