PC won't power up.

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bigcal916

Last week my son's pc started having trouble powering up. It was a hit/miss thing where sometimes it would power up when you pushed the button, sometimes it wouldn't. Well it finally stopped powering up a couple of days ago. (no fans, no lights, no beeps, nothing)
I suspected the power supply, so I switched it out with the one from my pc (exact same model) yet nothing happened. The power supply from his pc did power up my pc, so its not the power supply.
Then I suspected the switch, so I switched out switches and even jumped the switch, nothing happened.
Ok, with the power supply and switch eliminated, I did the following:
1. Disconnected everything from motherboard and tried start-up with only the power going to the motherboard. Nothing happened, cpu fan doesn't even turn nor do any lights on motherboard come on.
2. Put memory card back in and tried startup, nothing happened.
3. Tested all other components from son's pc (hard drive, floppy, optical drive, etc) on my pc and they work.

After all this, the only thing I can think about is motherboard fried. I even tried resetting it by pulliing battery, nothing happens. Anybody with REAL KNOWLEDGE (no offense to anyone) have any suggestions on what else to check before I replace motherboard?
 
Check for shorts on the motherboard, specifically on the standoffs that it rests on if they're metal. Is the cpu fan spinning and could the cpu have overheated?

That being said, you've done a remarkable job of troubleshooting.....all the steps most here would've suggested and it's probably the motherboard, as you've already surmised.
 
Masque, I checked the standoffs, they're all there. Nothing spins or happens anywhere when button is pushed.
1. power supply checked out ok, it powers other system but other system's power supply won't power it up
2. outlet and power cord ok
3. all other components ok.

The motherboard just doesn't seem to let any power get through to the system. As everyone knows, in atx systems, there's no direct power to anything. the motherboard controls it all, not like the old systems where you had direct power to the mb.

I don't see any burned spots on the mb nor do I see any bulging or bent transisters. I'm at a loss.
I'm leaning heavily towards a fried mb. But would a fried cpu stop power from being distributed throughout the system too?
 
Come on, I meant capacitors. I'm looking for some real help here and all I'm getting is smart remarks. I really would appreciate some help.
Question, would the cpu stop all power from being distributed throughout the mobo?
 
no one here can judge your level of expertise. Say what you mean to say.

No - your cpu does not stop power distribution. It consumes power.
Your PSU controls power distribution along with your mobo chipset.
 
Tedster, from what I could narrow it down to, it must be the cpu. The power supply checked out. put in a new motherboard but same cpu and had the same problem. decided to use a jumper on the main connector from the "power ok" pin to the "power on" pin and everything worked. So it seems like something was keeping the "ok" signal from reaching the power supply and letting it distribute power. Since a new motherboard acted the same way as the old motherboard, I'm going with the cpu. All have been replaced and I'm waiting on my new power supply (24 pin , 4 pin 12v) to arrive. My old psu is a 20 pin without the extra 4 pin connector for the cpu.
Thanks for all the help.
 
i think there was a thread with a similar problem... I couldnt find it but I may be worth a shot to look for it

Regards,

Korrupt
 
UPDATE.....
It must have been the processor. After replacing both the cpu and mobo I'm up and running again. Then after I got it up and running, it started acting very strange. I started having read/write errors, mysterious crashes, the blue screen of death, etc. Well after about a week of research, trouble shooting, and reading microsoft's knowledge base (a great tool), it turned out that the new memory module I'd bought was bad. DANG! memory problems sure are hard to diagnose. I thought I could get by with discount memory (Viking Value Ram), but I guess you get what you pay for. I replaced it with Patriot Platinum Extreme Performance with the cooling shields. My pc SCREAMS!!!!
 
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