PSU fried?!?

Here's my problem. I just took apart my computer to clean it. It was in dire need, and I just got some new RAM sticks to put in it. What a perfect time to clean it. I took everything apart. Took all the PCI card out and dusted them. I took the graphics card out and dusted it. I even took off the fan from the video card and gave it a good cleaning. I had to put more thermal paste on, but I know I did that right. I did the same for the CPU. I took the heatsink and fan off and cleaned them good, then re-applied some thermal paste. Then I took off the front cover off and gave that a damn good cleaning. Boy was it ever dusty. So I'm back to where I started... only with a much cleaner computer. I install the new RAM and then I start plugging in the cords. Everything is in place. I plug in the power and turn it on. Nothing. My monitor doesn't even turn on. No fans start up. I turn it off. Check my cables. Everything is good. When I put the PSU plug back in again, and turn it on, I notice the greed light on my mobo go on, but that is it. So it is getting some power. But... I start to smell something. I quickly turn it off again. After some messing with it, I determine it is the PSU that is smelling. What's going on? Did I miss something? Is my PSU fried? Just before I started to clean it, my computer was running fine. Now it's not.

The only thing that is different from before I cleaned it was the RAM. The new RAM is weird. I already had 2 x 512MB sticks in there and I was about to add 2 more 512MB. The new RAM is from PNY, but the two sticks are different. The package says they are both the same DDR400, 512MB DIMM Non-ecc, but one stick has RAM on both sides of the stick, while the other only has 1 side filled with RAM. Could this have caused the initial problem? Even after I took them out, it still won't start.

Any ideas MG?!?

 

The first thing I'd do is check the connections to the PSU. All of them. Carefully. On one occasion, not being able to see what I was doing clearly enough, I mis-connected the power connection to a floppy drive. The connector ended up being offset by one pin. The result was that the 5-volt rail was connected to ground. The red wire burned up, and that PSU connection was quite literally toast. I cut it off and taped the wires.

Is your PSU toasted? Unfortunately, that's quite possible. But you'll want to find out why before you put another one into that system -- or you might lose that PSU too.

Not likely related, unless one of the new memory sticks was bad. Under some circumstances, a PSU will shut itself down rather than burn itself up.

 

I don't believe it was the RAM either. I was thinking that it might be an offset pin, but when I retested it, I only had the wires to the mobo connected. And it still didn't work, so I'm pretty sure it wasn't any offset wires. I'll reset all the PCI cards just to make sure.

One thing I find bewildering is that when I did just connect the PSU to the mobo, I did see the green standby light go on the mobo. So it was getting some juice.

You know... maybe I fried my CPU. When I was cleaning that, I did take off the fan and unseated the CPU. I then proceeded to clean it, but while holding it. I wonder if while cleaning it I got any thermal paste off my hand and on a pin or two of the CPU. That could fry it couldn't it? If I did that, would it also fry the mobo?

 

I would try your basics, start with removing everything that isn't necessary from the board, drop down to one stick of ram you know works, then if you pulled the wires from the mainboard (power switch etc) pull those off again until you are left with nothing but the mainboard, ram (1 stick) processor and fan, no pci cards nothing else, then once you are certain everything is plugged in, go back and check the connections. remove all of the molex connectors from all of your drives as well so you are only powering up the motherboard. If you didn't pull the individual leads off the first time don't do it now, but if you did put back only the power switch one and turn the system on. *be sure the heatsink and fan are seated correctly before you try this *there is a right way and a wrong way to place many heatsinks* if any thing happens now start assembling the computer one piece at a time, until you found the problem, or it is complete. Checking for boot after each install.

 

That offers some hope that the PSU is OK - or at least the 5v. rail is.

Unfortunately, that possibility exists. Thermal paste is not usually conductive, but anything between 2 pins is definitely ungood. Even where the thermal paste is not conductive, its presence will probably alter the capacitance characteristics. At the frequencies a CPU operates at, that can be nearly as effective as a short if the capacitance is significantly increased.

If that happened, would it take out your motherboard? I'd have thought the odds were low, but it certainly isn't impossible.

See if you can find some visual evidence of the source of the burning smell you noted.

And once you have the minimal setup suggested by thesunscreen, check the PSU voltages with a digital multimeter if you have one. Stick the probes in the back of the motherboard connector to check those pins. You'll find the pages here and here helpful.