Power on failing

[redfish]

Hey guys. Back again with yet another hardware issue. Here's what happened:

I just moved out of college for vacation and brought my rig with me. I set it up in my old desk at home and powered it on; the second monitor worked fine, but the primary monitor wasn't detecting a signal so I turned it off and checked the connection. Didn't see anything obviously wrong, although one of the nuts on the back of the GPU had fallen out so the DVI cable was only screwed in on one side. I unplugged it and turned the computer back on. It didn't.

I spammed the power button until I heard a click from somewhere inside the PC. There was obviously something wrong. I looked down to check for the green light on the mobo that indicated it was getting power; that little LED was on, so the motherboard was indeed getting power. I turned the PSU switch off and waited for the light to shut off, then I tried again. This time the lights and fans turned on for maybe half a second before shutting off again. I hit the power button again a few times and nothing happened.

This is more or less what happened every time I tried for some 5 or more tries. I'd unplug, wait for power to drain, plug back in, and hit the power button; lights and fans would flare up for less than a second then shut down again, and then nothing would happen when I tried hitting the power button again until after I had unplugged and let the caps drain again. Here's a list of things I've tried:

-Bypassing the surge protector and plugging straight into the wall
-Unplugging all peripherals, including monitors
-Holding power button down
-Holding power button down with PSU switched off, and then switching it on and releasing power button
-Unplugging one GPU
-Unplugging both GPUs
-Unplugging disk drive
-Unplugging CPU power
-Unplugging all case fans from motherboard

None of the above things caused any change. Here's a couple pieces of potentially relevant background information:

-This thing was driven in a car for a while. I just always get nervous with that thing in the back of a car. Wasn't a horribly bumpy ride, but it did involve a detour off of the main road.
-When I moved out, it was probably the first time I've actually turned it off in months. I've more or less left it running since I got to college.

I also have multiple motherboards, GPUs, CPUs, and RAM that may or may not be functioning tucked away in a closet somewhere if they are needed for troubleshooting.

My suspicion is that something's shorted somewhere. I hope not, because I feel like that would have already caused irreversible damage.

Can somebody provide any assistance? I've pumped a lot of money into this thing and now is really not the time for it to be down for a while... I would really appreciate it.

 

[redfish]

Update: no clue what was happening before, but I just tried again after waiting for a bit and it turned on just fine. Fixed the monitor issue by swapping DVI and VGA cables. I'll post if it has problems turning on again.

 

[patonb]

Weird. Maybe humidity from moving shorted something. Maybe a part shifted.

 

[redfish]

It's doing it again... Ran fine until now cause I never turned it off.

Update: I popped open the back panel and it powered on; I then turned it back off to change a PSU setting and now it won't turn on again. This is gonna take all day if it just takes a random number of tries to work.

 

[redfish]

So.
I hear a click sound coming from what I thought was the motherboard after I turn off the PSU, but only when I've tried to boot. When I turn the P/S on and off again I don't hear it. Along with the click, the light turns off suddenly after a few seconds, as opposed to fading out when I haven't tried to boot. I now think that click is coming from the PSU.

I tried unplugging all the cords directly from the PSU, since it's modular. I've unplugged every cord except for the motherboard and it still does the exact same thing.

These tell me there's a short somewhere in the motherboard circuit. Can anybody help me figure out where it might be, based on the fact that it occasionally boots up without problem?

 

[patonb]

You may want to reseat your motherboard. The board may be ground out somewhere, so though it's a pain, remove your board, test run it on a piece of cardboard to see if it'll boot routinely.

 

[redfish]

I'm gonna let it sit for a while and take a nap in case I can get that random power on, but I'll give that a shot if I can't get it to power on. I'm just a little hesitant since I'm at school and don't have any of my gear with me.

 

[redfish]

I have this thing lying on a cardboard box on my floor. The only things connected to each other are the motherboard, power supply, RAM, CPU, and CPU cooler. No difference from fully assembled computer. The power supply's fan flares and stops along with the motherboard-controlled fans and lights. Any clue what to do next?

Edit: I just did a manual dry test of the power supply to see if it turns on; if I keep the power on and common pins connected the fan runs.

 

[patonb]

You have access to a multi-meter?
Could be a shorted motherboard internal trace.

 

[redfish]

How do I test for that? I don't have one right now but I might be able to borrow one from my lab.