Optiplex GX280 power issues

[frank5754]

I am working on a Dell Optiplex GX280 (clamshell case). System would not power up. Checked power supply with Dr. Power by plugging 20 pin connector into tester. Testing shows good power supply and when 20 pin is connected to tester and everything else from power supply is connected to system, hard drive spools up, power supply fan comes on etc. When 20 pin connector is re-attached to mobo, I get no response at all other then mobo led coming on. These GX280's are notorious for bad mobo's due to leaking capacitors, so I picked up another mobo off e-bay. It looks good capacitor-wise and when I put that in I am still getting the same results. Any thoughts out there?

[Steve R Jones]

These GX280's are notorious for bad mobo's due to leaking capacitors,

I gather the second mobo wasn't a new one??

What's the history behind the pc...Working one day - quit the next?

[frank5754]

This is one of several pc's used as terminals in restaurant. They have some gx270's and 280's. This one was an extra unit that they had. The replacement motherboard was ordered off of E-bay and was supposed to be new, but you know how that goes.
When the main connector (20 pin) is connected to the board, the mobo led comes on, but no response when I try the power switch. If I hook up the 20 pin to the tester while all other power supply leads are connected (hard drive, etc.) the power supply fan comes on and the hard drive spins up. I'm thinking it could be as simple as a bad power switch, which I will try, but I was wondering if there is anything I am missing.

Thanks for answering my post

Frank