Computer boots up fine but cpu, psu and chassis fan do not work

Hi, I recently installed a new chassis fan (LED Which required to be plugged into psu, old fan only required motherboard connection).
I took the LED fan out of the system completely and put the old one back as i could smell some burning, now the cpu, chassis and psu fan won't move as i start up the system, the computer boots up fine, but it over heats as you would expect, I don't even get any error relating to anything not working.
The computer is a Compaq Presario 5000 desktop.

I've upgraded systems before but have never encountered a problem like it, could it be the psu on its way out? maybe i've shorted something? I've doubled over making sure everything is connected but everything seems to be in order.

 

It sounds to me as if you'v burnt out a 12v line in psu somehow,the psu fan is temperature controlled completely seperate from the cpu fan controller which is controlled by the motherboard,the only thing I can think of is a dead 12v line,I dont understand why it still boots

Yeh I agree get a new PSU

 

If it isn't the PSU then do a very careful inspection of the MOBO. I suspect you've blown one of the 0-ohms resistors, that are inserted in series with the 12v line. Yeah - zero ohms sounds a bit odd, but on server boards, these are actual mini-fuses that can be quickly replaced. On retail boards they look like a teeny tiny resistor and if your eyes are any good you might even see a single black line around it's belly. There may be other designs that I'm not aware of so let your nose sniff around on the surface. With luck you'll smell the burn spot and then you can either replace it with a zero-ohm resistor or a fine strand of wire. I prefer the former for mobo safety, of course, but the wire will get you running again.
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