Toshiba l300d blank screen, lights up and fans ok

i am having this issue and have been up all night working on it,
the toshiba satellite l300d with amd cpu was showing a black screen while responding otherwise, (lights fans etc) no response on an external lcd,
tried replacing memory, cpu, and removing all else. removing charger, holding down power switch for a minute, restart,
no response on the lcd,
cleaned off old cpu paste, applied new, cleaned nvidia chip with isopropyl etc, put in the original cpu, tried again, it worked.
started adding one item at a time and restarting, got past the hard drive and booted into windows, all fine,
put in the mini pci-e wireless card and it gave me a black screen again, removed the card and it switched on fine, thought i'd give the wireless another try and it gave a black screen again, and now it keeps giving me a black screen regardless.
i've shorted then even removed the cmos battery, reset the bios, drained the power switch for 1 minute again - no results,
:confused can anyone give any guidance on the issue as i'm not planning on changing the video chip or heating it up since i've seen it switch on ok and have a feeling that the wifi card has jammed something up - all the pins in the wifi slot are straight and none are shorting,
peace,
abz

 

I see it's an old post, but just to help anyone else looking. You would be better off looking elsewhere for Technical help, as MajorGeeks seems to be only useful for downloading Software. Apart from very simple problems, the advice on these forums is either non existent, or is a guess. Hope this helps someone.