On Wednesday, November 8, 2017 at 8:57:33 AM UTC-5, wrote:
I think you probably have burnt toast.
I usually bench test the power supply by connecting green to black or what is appropriate for your psychological
This turns on power supply and you can test all the voltages
When you press the power on it basically does this if in unit and when you power off a SCR on MB turns off connection
There is always a signal there from psu to turn on unit.

The switch itself on computer goes on atx to the screen circuit
That circuit can go bad
You can make a jumper so power supply is always on if a bad sensing circuit

Also many of these units have video card integrated and if it is bad you will see no post
I have had internal video cards go bad on quite a few dell's
Sometimes just adding a cheap video card will do the job.

The fan in the psu should turn if it is powered on by jumping and the internal fan not the cpu fan should also run if PSU is OK
The internal fan is usually not dependent on MBA

I would try a cheap video card and use a psu u it set to be on
If nothing the unit is toast

By the way Ben Hello from .
METRONID

Long time no hear, METRONID!

Indeed. The power supply is a BESTEC, with a world-wide reputation for crappiness. Any time I see a BESTEC, I hasten to replace it and make sure nobody can ever use it again. And that's even if the Bestec is actually still working. Not exactly a tribute to product quality... Ben Myers