Re: Optiplex 755 only turns on through power supply button, no video output.
1. The power button LED is yellow. Like I said, the power button only works if you hold the power supply button down first. However, if you hold the power button down alone it flashes yellow.
2.. Yes, it stays lit. It also stays lit after I turn it on the aforementioned way.
3. The only peripheral I had attached was a VGA cable to monitor output. Removing it does nothing.
4. The system is stock as far as I know.
5&6. Removing these still does not allow the computer to be turned on through the power button alone. I must hold the power supply button first and then press the on button. Still yellow LED power button, no diagnostic lights, and no video output.
7&8. I removed the CMOS battery. I wasn't sure what the I/O Panel Cable was, but I assumed it was component 8 described on page 5 of this link:
I plugged the power cable in and it did not try to turn on by itself, there was no beeping either. The power supply test button still works and turns the power supply LED green, however.