Will the wrong power supply kill a mobo and everything connected to it?

I got a 400watt power supply from from ebay to replace the 305watt PSU in my Dell Optiplex GX280.....
I connected a new power supply incorrectly to the main motherboard connection. Plugged in the 20 pin into the right side of MB 24 pin connector (forced it in!), when I should have plugged it into the the left side, then add the additional 4 pin next to  the 20 pin. (the 400watt power supply is compatible with both 24 and 20 pin motherboard connections, of which I did not know at first). After I made this error, I turned on PC---and nothing works, other than yellow AUX light on mobo and fan works on graphics card. So, I re-installed the original PSU of 305 watts, and again---nothing works, no PSU fan, no CPU fan running. So the question is : Did I fry the mobo with everything else connected (RAM, HDD, CPU, etc.)...Or have I only killed the motherboard ITSELF?...I need to know whether to buy a new motherboard (Dell OH7276)...or just buy a new PC altogether.

Dell Optiplex GX280 Tower, 3.4Ghz, 3GB RAM



Re-design7 years ago
SAme answer you got when you asked this two weeks ago.  The only way to tell what's burned up is to try each piece on a working computer one piece at a time.  Of course you are taking a chance with the good computer.  Every once in a while when a component fails it fails in a way that is destructive to other components and may cause damage when you try it in a different computer.

Good luck.
ddavel544 (author)  Re-design7 years ago
And here's the up-date: Got another DellOptiplex GX280, 3.6Ghz CPU (used from Ebay), but it only had 512 RAM and no Operating System. So, I installed the 3GB RAM from the 'dead' Opltiplex, plus I installed the SATA Hard drive... also from the 'dead' Optiplex, which has  Win XP PRO. And I even switched the cheap ST DVD/CD that came with it, for my old Samsung TSST CDW/DVD.... And "well-a"....now I got one freakin' FAST PC!...Seems like the mobo on dead PC is the only problem, not running fans, etc.. But I suspect, it may not be dead at all...I checked some sites that talked about a default 're-set' switch on mobo's...but I just can't find that switch on this motherboard. May have to take it apart to find that tiny switch. No sweat...I got time.
ddavel544 (author)  Re-design7 years ago
Thanks for the response Re-design, I have already switched out the COSMO battery from the 'dead' Optiplex and put it in my old faithful, but lame, Dell Dimension 2300, which is what I'm using now. And the battery seems to have improved the overall performance of this PC. Also, have already bought another Dell Optiplex GX280 with a 3.6Ghz CPU, 512 RAM and 40 HDD ($111-total from Ebay), which will arrive in 2 days, and I had to buy an OEM Win XP PRO OS for that PC. So once I get that up and running, all I have to do is install the full 3GB of RAM from the dead PC. And maybe even attach the 40 SATA HDD from the dead PC to the new one. If the COSMO battery is working as it is, I think everything else should be alright. Will keep ya all posted as to success of failure of this "experiment". After all, this will be the last computer I will ever buy!---I'm through with crappy Ebay!
I'd suspect you've killed the whole thing. Just bin it.