No one else seems to know. I am guessing that it is the BGA Video Chip because Caps, Resistors, Diodes have to do with bringing power to specific components. I have purchased some crap boards off ebay and was planning on trying to extract the video chip using a pencil torch, if it seems easy enough I would try and do it with this board. I would just like to get this thing up and running cause the resell value is excellent on this laptop.
Looking at your post, funny but I have another T-40 I am working on, same problem as yours. It is working one minute and I lose video the next. I am not moving the machine when I experience this problem, nor am I punching keys. The lights stay on but nothing on video. I have not tried to plug it into an external while this problem is happening but next opportunity I will try. If I get nothing on the external, even after the function F7 key is pressed I will have to assume it is an intermittent problem and will consider heating up the board to reflow some of the solder welds. What do I have to loose at this point.
Oh also when the screen goes dead I turn the system off and right back on and all is good almost like it did not even happen. Really strange.