DescentBB

So in 20 years of putting together all my different computers, never have I had one put out a puff of smoke...until now. Trying to figure out where it came from and what caused it. The curious part, after pulling the plug and searching around I didn't see anything obvious. So I plugged it back in, saw the mb had power via the on board switch lights. Hitting the one switch didn't do anything but when I hit the onboard reset switch, it powered right back up. Screen went to dos messages about windows not shutting down properly, hit "start Normally" and it did. Booted back to windows, checked CPU-Z and everything seemed normal. Started Skyrim back up and entered game just fine. So one worry about cpu frying seems not a issue.

Here is the odd part. When I now shut down normally, it will not restart by pushing the on button. Looking inside on the MB (ASUS P8Z68-V Pro/Gen8) the reset button light is not on nor is the indicator light for the memory. The light for the power switch is on and when I push it the system powers on and boots up normally.

So any direction I should be looking at with these minimal clues?

It smoked from where? Back of the PSU? Any accompanying pop or bang?

There are components around, especially in and around the PSU where current levels are high enough that if a solder joint broke the electricity could arc across the cracks and that would smoke easily enough. Similarly a loose connection on one of the mains could do it too, anything that feeds the CPU or the video card can easily pull hundreds of watts and that is plenty to make a plug smoke if it has a poor connection.

Yeah, I'm banking on a cap going off in the CPU with no lights or even a blip. The caps in the PSU are huge and have (typically) some kind of oil in them.
Occasionally, someone at work will install one backwards and it will get past the normal checks. Then the unit is housed and build up and put into highpot, the cap goes pop! (Or fizz) in either case it releases a small cloud and the area needs to be evacuated for 30 minutes or so.

Try another power supply woody and see if that helps.

Well it doesn't seem to be the power as once I push the mb power on switch the comp. starts up normally. Even played Skyrim for a couple of hours. Don't remember a pop, just the comp started to disco and when I looked at it, smoke was coming out the back exhaust fans. So the only hint right now is the main box "on" button does not turn comp on.

Well, some video cards do vent out the back too, so I'd check around the power regulation circuits on yours for any burn marks. Venting that much smoke should have left a mark or a trail somewhere. Otherwise it is probably in the PSU since that is about the only other place where a large quantity of smoke could be generated without immediately cooking the system for good, I'd pull it and shine a light through the vents/fan, look for burn marks around where the power leads are soldered in.

As for the power switch not working, although it is a soft switch and never carries any actual current just like the one on the motherboard it wouldn't be a bad idea to inspect the wire and the switch, see if they have shorted against something. Probably a good idea to pull the whole computer up on to a desk and poke around with that light. Burst caps to the point of smoking would have put out a very obvious burning electronics odor that nobody would miss unless they had totally lost their sense of smell, so I'd lean away from burning capacitors for the moment, but definitely give a solid look over of all the power leads, especially the ones that deal with a lot of wattage like the PCIe leads for the GPU, and the Aux power for the CPU.

Your computer is getting high. Look around on the floor for the joint it's hiding.

Well I looked at the caps on the MB and didn't see any bulging or scorch marks. Checked the on switch button and it now works. Comp seems to run fine so I am at a loss to what happened. Power supply is on bottom of case and has it's own exhaust fan. Smoke came from top of case and at rear. I also have side exhaust fans venting out near the top of the case but no smoke out of them. So only thing really venting at top rear is the vid card and the cpu fan (a big Zahn fan).