Optiplex 7020 not turning on

bad psu is not excluded at this point.  what is power button led code?

try reset CMOs settings

Locate the 2-pin CMOS jumper labeled RTCRST on the system board. Move the 2-pin jumper plug from the password jumper to the pins on the CMOS jumper. Plug the power cable to the computer and wait for 10 seconds for the CMOS to clear.  Disconnect the power cable from the computer.  Move the 2-pin jumper plug back to the password jumper.

#21 RTCRST jumper connector

#19 password reset jumper

also replace CMOs battery with new one ($1-2).

Did you get the green light on the back of the PSU when pushing test button?  That means your peripherals are ok.  A bad PSU can still power the fans when test button is pushed.  Likely bad PSU at this point.  It's not too surprising as initial mfr. date for the 7020 was 2014.

I had the same problem. Power button on the front stopped working and fan was not spinning up.  Looked like a dead PC.  I then found that I can manage to get the PC to power up by holding down the test button on the back of the supply (which lets the fan spin up) and then pressing the power button on the front of the PC while still holding down the test button on the back of the PC.

Its almost as if the burst of power from holding down the test button lets the power button on the front work OK.

I don't know how long that is going to carry on working.  It has worked reliably the few times I have tried it so far.

If not already, I'd make sure everything important is backed up outside of the PC in case the PSU goes.  Then your files are still available while PSU is down and/or it makes an easier transition to another PC.*  *Unless SSD's/HDD's are simply moved.

I found out what the problem was on my machine.  One of the front USB ports was broken and had a short.

A USB socket has a bit of plastic holding the 4 USB pins.  That bit of plastic had snapped off from the socket, so the 4 pins were not attached to the plastic (the plastic was not even there) and the pins were just "floating" in air.

This means the pins could be bent out of shape (and also that I could insert a USB plug in the wrong way around by mistake).

When I put something into that socket earlier in the day, it badly bent one of the outer USB pins (that would normally be 5V) so that it was touching the outer metal part of the socket which I assume is grounded.

Once I straightened out the pin and got rid of that short, the power button started working again.

Glad to hear you got it working.  Definitely not used to a USB short acting like a PSU on its way out.

Accept as Solution"

Thank you for your posting.  I had the exact same problem and your instructions fixed it. 

Now I need to find out how to replace the damaged usb port.

I take it that it's a front USB port that's damaged.  In which case, replace the front I/O panel.

You didn't say if you also have a 7020 and what form factor/size it is; however, front I/O panels are easily had on eBay.