t1700 mt no display

Re: Several T1700s failed to post after A25 Spectre bios update / no video signal

Dear Dell Users

I have a similar problem

Bought a used t1700 with german w10pro
Updated to A25
In Setup in BIOS changed boot sequence and allow strong passwords (not having set any)
From that moment no screen activity
pc seems to start normally no error codes blinking
display remains black so cannot enter setup f2 or boot f12 as I do not see anything
tried other videocables other displays took out videocard
tried build-in vga and dp ports
does someone have a solution for rebuilding bios ? video drivers ?
thanks a lot arthur the netherlands