Optiplex 9020 power, boot failure

First try using a new size 2032 CMOS battery:  How to Perform a BIOS or CMOS Reset and Clear the NVRAM on Dell Computers 

If no luck, then:  How to Run a Power Supply Unit Self Test On a Dell Desktop or All-in-One Computer 

If it helps:  Dell BIST Test video 

"Dell OEM unit" is referring to Dell PSU.

Greetings,

     One would think so but when all it said and done no led on bist is on unless I push bist and no activity on front panel.  Machine is dell OEM??

Greetings,

     Thank you for the quick response. I have no power led on the power supply when plugged in to the wall.  FYI new power supply(I replaced it thinking it was causing my power/boot failure). I did go through the b.i.s.t. diagnostics i.e. unplugged everything from the motherboard.  When I press the b.i.s.t. I have solid green led and all fans turn on, but no response from the front panel or power led/switch.  According to the b.i.s.t., the motherboard and processor are receiving power.  I have reset the cmos, password, etc.  I removed the rtc battery and tested 2.78vdc(in range).  I have removed the ram and powered on but no led on b.i.s.t.  Is there a sensor in the power switch, front panel circuit that could prevent the motherboard from acknowledging power supply from working??  Should I bypass the front panel/power switch to diagnose??

Please help.

"Is there a sensor in the power switch, front panel circuit that could prevent the motherboard from acknowledging power supply from working??"  No.

What is in it for a PSU now?

With all external peripherals disconnected, with everything in place inside of unit, if you push test button on PSU (with PC powered off) it should mean internal peripherals are good.  This is if you're using Dell OEM unit.

Greetings,

yes, the PSU is dell OEM. The original is still here and might not be defective after all.   I replaced it thinking it was the cause of my power on failure, regardless the bist doesn't light up the LED unless I push the test button.

Best regards