Well, through some experimentation I think I figured it out.
I did measure the common driver outputs of M11 on the O'scope and all seemed fine. I took the LCD back apart and toned out the traces of all the common drivers which go to all the pads on the four corners of the LCD. All the connections were good. On a whim I rotated the LCD glass 180 degrees and put it back together. Now the missing rows were at the bottom of the screen. This shows the LCD glass is a simple matrix and that the driver chips are all good. I finally pulled the zebra strips off the glass and cleaned the other side, cleaned the glass and after a few more attempts got it back together with things lined up and all but the original three rows working. Amazingly the bodged in replacement for the missing LCD contact pad held up through taking the assembly apart 8-10 times. So, only the one small missing vertical line was fixed. But I learned a lot about how the LCD works and that if you have nothing to lose, rotating the glass 180 can make for a quick check if the problem is LCD or driver. I wonder if the LCD glass is the same as the M100? Jeff Birt From: M100 <[email protected]> On Behalf Of Jeffrey Birt Sent: Saturday, August 29, 2020 3:15 PM To: [email protected] Subject: [M100] Questions about M100/T102 LCD operation Hi, I'm tinkering with a T102 LCD that started out with three missing rows (5, 6, 8) and one missing vertical line at the bottom right of the screen. I tried a good LCD on this computer, and it worked as expected to the issue(s) are with this LCD. Having nothing to lose I filled the metal frame off and found a partially corroded pad on the bottom. I was able to fix that (a stroke of luck!). I then cleaned the bottom of the zebra strips, I did not try to pull the strips loose from the glass itself though, I also cleaned the contact pads on the PCB itself. After reassembling I found the missing vertical line was now working, which is more than expected. The three missing rows (5, 6, 8) counting from top of screen are still missing though. After reading through the LCD section of the manual again it is my understanding that M11 and M12 are the common drivers for the rows. It looks to me that M11 handles rows 1-20 and I'm assuming that row 1 is at the top of the screen, this seems to make sense looking at the LCD. I've checked continuity from the outputs of M11 through the vias. I think next, I will try to measure the output signal levels to see if they differ for the missing rows. If the M11 outputs seem kosher, then I guess it comes down to a connection issue through the zebra strips or a bad LCD itself. As I will probably only get one more shot at taking this thing apart and putting it back together before the metal retaining fingers are too fatigued, I wanted to run this by the group to check my thinking so as to make the most of the last attempt at taking the LCD assembly apart. Thanks, Jeff Birt
