Here’s the dealeo, my daughter’s computer won’t start up. The LED on the MB lights up, the on/off power switch does nothing. I tested the 24 pin connector with my multimeter and all of the wires fall in range of what they’re supposed to. I shorted pins 15 and 16 and I heard the power supply fan come on.
Could this still be a power supply problem? From what I’ve read it’s really unlikely that the switch is bad. Of course I’m hoping to hear anything that indicate the mother board isn’t trashed.
0Have you tried turning the computer on without the power switch? (just short the two pins the power switch is connected to)… Also, did the motherboard work before (just installed it, or was it a working computer)?
Nothing happens on the motherboard? No fans spin at all? Anything new added (new RAM, cards, etc)?
I think it unlikely. What was the last thing you did inside the tower? This happened to me when I took my processor off to show my dad (We were thinking about replacing it.) and I didn’t get all the way back in. Once I fixed that, my computer was back to its old happy (if slow) self.
It’s a Dell that’s a couple of years old. My daughter said there was something wrong with it (that it wouldn’t start). I had her bring it into my office. It started up with no problems. I cleaned it up, updated her AVG, etc. etc. Told her that I found nothing wrong with it.
Fast forward two or three months, she says it won’t start up again. Same routine, brought it up to my office, it won’t start. I opened the box up to check out the power supply to unplug/plug in all the connectors and to test what I could of the power supply.
The switch itself is mounted on a silicon board. I wasn’t sure where to short across on it, but I touched a wire across the two soldered protrusions on opposite side of the switch where it’s attached to the silicon board. Nothing happened. 
Beware that Dell PSUs aren’t always standard ATX.
Do you have a PC speaker attached so that it would beep if the motherboard is registering an error code?
Wow, I’m surprised I didn’t think of that. No, I didn’t hook one up, but I will when I get back home. Further proof that it’s been a looooonnnnggggg time since done any kind of hardware work on a pc.
I’m not expecting much… it behaves like it’s dead.
Definitely sounds like it might be a power supply issue.
Another possibility: a loose connection. The fact that it wasn’t working in the original place your daughter had it yet it worked in your office says that something got “jiggled” in transit and was able to make the proper connection.
You also may want to look at environmental factors. Is she in a dusty/hot/cold/humid climate that’s different from your office?
One thing to always check whenever you’ve opened up the case is that everything is still seated properly (cpu, ram, power cables, any add-on boards, etc).
If you’re up for a down-and-dirty diagnosis, I would suggest an out-of-case build, so you can rule out all extraneousness factors.
… and to throw a spanner in the works, when I worked at a computer store, my co-worker regaled me with a story of how a client’s PC never worked at home, and always worked when she brought it into the store. As it turns out, her house circuit was just a little off 110-120 volts, and the computer store’s line-conditioned, battery-backed-up, unit was just fine for the computer 
Ha ha, that’s too funny, and actually it’s not too far off from what I was suspecting at first. I figured my daughter just didn’t have it plugged in properly, or something. When I opened the case there was a TON of dust bunnies. in there. I’m hoping they didn’t wreak some sort of havoc in there.
Spanner?
Out of case rebuild? Give me more details about an out of case rebuild. I have no problems pulling the components to check them… but I don’t see how that would help.
Spanner = Wrench.
Depends on which side of the pond you’re speaking from.
A year ago I was called out to a lady’s PC, same thing, power but nothing working. I pulled the 2 RAM sticks and put them back. The thing powered up, no problem.
She rang me again the other day, so I did the same thing. It didn’t work, but removing and putting back her graphics card did!
I’ve also had instances of cases going rogue, see the earlier post about building outside the box. In one instance I lost 3 motherboards before I discovered that something in the case was shorting them out after being on for 30 minutes.
These are all easy tests. If that doesn’t work then you may have to consider testing with replacement memory, CPU etc.
BTW most Dell’s have a row of 4 diagnostic lights at the front or back, which should all be green. Maybe yours has too. Cheers, Col.
I have seen quite a few machines fire up with a new supply even where our psu tester called the PSU good or marginal.
I’ve heard a lot of people say this. I may just buy a new one. It won’t be the end of the world if I waste $50 or $60 bucks I suppose.