PSU Question

[Makavelli]

Mother in law has an emachine that conked out on her. I turned the psu on and it was making a ticking noise but did not power up computer. Unplugged the atx connectors from the mobo, turned on the psu (plugged a power lead into the back of it) and put my multimeter across the red and black on the 20pin connector and the yellow and black on the 4 pin connector - no reading whatsoever. Left the psu with the power lead in and unconnected to the mobo and after a couple of minutes smoke started coming out of it what i want to know are 2 things.

1. Is it all right for the power to be going into the psu when it is not connected to anything?

2. In hindsight i think i went about testing the psu wrong - am i right in thinking that i won't get a reading until i short the 2 pins that allow the atx to turn on without the mobo.

I have googled emachines and i have read a few bad reports the problem for me is i upgraded the memory before all this happened, although the computer posted and ran fine for a couple of days beforehand. It seems either the psu fried and took the mobo with (i tested on another psu and the psu wouldn't even power on when connected to the mobo) or the mobo fried and i took the psu out by running it without a load.

Any thoughts?

 

[semi-pro waster]

You shouldn't connect the PSU to the power without some form of load on it, even if it is just a fan or two.

I'm not sure about what exactly you would need to do to get a reading, I'd personally have left it connected to the motherboard and then done the reading, it isn't likely you could have damaged the motherboard any more.

 

[Joe42]

All decent psus should behave perfectly with no load.
Emachines are a budget pc maker, so unfortunately can't afford to include decent psus.

You will need to start up the psu before you measure any voltages yes.

Tbh i would replace the psu whatever readings you get, particularly if its been emitting smoke and ticking.