black screen after update

This is the second time that I have had an issue with black screen at start up after windows update. I have an optiplex and I don't even get the dell symbol when I power on.....I have tried hitting the F12 button repeatedly but to no avail and all of the current 'solves' on google don't apply as I can't access BIOS.

It appears as if it is not completing POST...so many solves are for boot issues.

The last time that this occurred I stumbed across a 'solve' that required me to hit several keyboard control keys at start up to almost reset the display driver or something...I did try to remember this thinking it was a combination of ctrl, alt F11 or ctrl, win, shift P....I can't remember or even find the link that I used!!!

As I said...when I did this last, it got the computer past the post to the dell sign at which I was then able to hit F12 to run the diagnostics and fix the update issue once the computer had booted.

Its really frustrating...I only have a back up laptop which I tried to connect via HDMI to the optiplex as I don't have a second monitor.it didn't detect the compture...should I try this with a s video cable instead???

I am really at my wit's end as nothing online is relevant to my situation as a solve and I need to access my assignment which is due next week!