I have two Optiplex 790 SFF systems, both out of warranty.
One system displays the yellow flashing power LED and does not power on when the button is pressed, which I know is due to a PSU failure and therefore I will replace that.
However the other system has been working fine until now whereby it started to complain there was no bootable device found, after which it would power off by itself before I could press F1 or F2, but now when I press the power button it comes on for a few seconds (POST lights flash on/off) but then powers off and does not come back on when the power button is pressed. The power button does not flash when pressed, it just does nothing. Disconnecting and the power cable and reconnecting it a minute later, there's no self-test, and pressing the power button does nothing. However, leave the power disconnected for at least 5 minutes and reconnect it, we get a very brief self-test, and the power button now responds, but the same behaviour repeats as in it powers off after a few seconds and the power button no longer responds.
I've seen the first issue numerous times but the second issue has me stumped. I don't know if it's a dodgy PSU or something else. There's no blown capacitors on either board and on the second machine both the incoming and CPU fans are spinning up, as is the power LED on the DVD drive, until it just dies.
Any ideas as to what could be the problem? Is it's a dodgy PSU, I'll order a second one, otherwise if it's anything else it might just be cheaper to buy a new system.