Double fan death or eletrical problem?

[krnmastersgt]

I currently had to swap out my Ultra 700w PSU since it seemed like something was burning on the inside, after a quick power up to see how well it was working I saw that neither of the 80mm fans was spinning at all, but for all other purposes seemed to be just fine.

So I'm probably going to go buy a spare 80mm if I can't find one lying around my house and pop it in to see if that's spinning and I just got unlucky with both fans dying at the same time (as far as I can tell, one might have been enough without me noticing) was the problem
or
If perhaps a short created by dust ruined the circuit that powers the fans since it seems isolated from when I opened up the PSU (was gonna be too much a pain to get them to cover under warranty). I didn't really examine it since I was pressed for time but I probably will tonight or tomorrow since I have a bunch of free time.

What's more likely and would this still be safe to use all the time in a system? Opinions much appreciated. (also appreciated would be how to force the PSU to power up without hooking it up to a system so I don't risk the system, but I don't particularly think it's gonna bust on me and take out a system)

 

[Modelworks]

Fans in a pc are not like house fans that run on AC current. The fans in a pc are switched. Inside the fan is 4 separate coils of wire, the chip inside the fan switches on and off these coils so that the shaft the fan blades are connected to is pulled forward to that coil. Then it cuts that coil off and turns on the next one in the series, pulling the fan blades forward again. Repeat several hundred times and you turn the fan.

The fans like in a pc do have one advantage, they are much harder to burn out from stopping the blade from turning than AC fans. So damage from dust stopping a fan is less likely.

Because that circuitry is required inside the fan it can burn out , short out and fail any way that anything else using a transistor can fail.

 

[Zap]

Maybe the fan controller burned out? I've seen cases where the fan either stopped working or just went full speed all the time.

 

[roomak]

I have same problem. Fans stopped working yesterday. I've checked both fans and they're fine. Problem is in the thermal controller. But I don't know how to check thermometer and transistor. Probably I will just connect fans to +12V and have them running full speed all the time.