CompaqSniffer
Experienced Member
The title says it all I'm trying to figure out how to replace the plasma screen of the Compaq Portable III with an LCD. The reason why is because I'm in the midst of repairing some and they are very finicky. Very finicky actually doesn't even begin to describe the Amount of frustration I have experienced trying to repair these things. I have yet to fully repair one, as all screens I have took a crack at have this weird flickering horizontal line issue after I have repaired them. I have spent literal months trying to fix multiple screens.
Today I attempted a repair that only had 3 dead horizontal lines. I managed to fix all of them, but when I left the screen on for a few minutes, BOOM! Bright vertical lines show up out of nowhere...
Suffice to say I've had enough, and I want to know if there is any way I can take the internal video signal and hook it up to an LCD.
I've done so much research myself to see if it's possible but every Google search leads to a dead end. I find myself going to the 20th page of google every time I try to find an inkling of information to try it, but no luck.
Some info that may be helpful: the Compaq Portable III uses the same plasma screens that the Toshiba laptops do, albeit with smaller video cable connectors than the Toshibas. I'm pretty sure that the plasma screen controller board is a digital to analog converter, and that the video signal may actually be VGA, and not CGA or EGA. I don't know for sure though. The video signal I'm positive is digital before it hits the controller board, and that this info could help.
Knowing this, would there be a way to figure out what the video signal is, or find a way to hack the controller board to grab the analog signal off of it if it has one? I've done a few composite mods but I don't know how to grab a VGA/cga/EGA/MDA signal, or what it would look like on a scope. Also my scope is from 1960, so it's bandwidth is pretty low for what I'm trying to test. I'm only 21 and I'm still somewhat brand new to electronics/vintage computing. I've only been doing it for a few years now, so even though I know my way around a soldering iron, I lack the hardened experience of many people who have this hobby. I was wondering if anyone would be willing to try to probe the signals who has experience with this kinda thing. I'll post pictures of the controller board in question, and a few others as there are multiple revisions. I wanted to know if there is any standard type of video signal I could grab off of this thing or the internal video connector. I know I could take the external signal, but I didn't want to have to switch the video signal every time I turn it on, plus I haven't the clue if the switching actually works, because pressing Ctrl shift < or > doesn't do anything noticable like it does with my Compaq Portable I.
Today I attempted a repair that only had 3 dead horizontal lines. I managed to fix all of them, but when I left the screen on for a few minutes, BOOM! Bright vertical lines show up out of nowhere...
Suffice to say I've had enough, and I want to know if there is any way I can take the internal video signal and hook it up to an LCD.
I've done so much research myself to see if it's possible but every Google search leads to a dead end. I find myself going to the 20th page of google every time I try to find an inkling of information to try it, but no luck.
Some info that may be helpful: the Compaq Portable III uses the same plasma screens that the Toshiba laptops do, albeit with smaller video cable connectors than the Toshibas. I'm pretty sure that the plasma screen controller board is a digital to analog converter, and that the video signal may actually be VGA, and not CGA or EGA. I don't know for sure though. The video signal I'm positive is digital before it hits the controller board, and that this info could help.
Knowing this, would there be a way to figure out what the video signal is, or find a way to hack the controller board to grab the analog signal off of it if it has one? I've done a few composite mods but I don't know how to grab a VGA/cga/EGA/MDA signal, or what it would look like on a scope. Also my scope is from 1960, so it's bandwidth is pretty low for what I'm trying to test. I'm only 21 and I'm still somewhat brand new to electronics/vintage computing. I've only been doing it for a few years now, so even though I know my way around a soldering iron, I lack the hardened experience of many people who have this hobby. I was wondering if anyone would be willing to try to probe the signals who has experience with this kinda thing. I'll post pictures of the controller board in question, and a few others as there are multiple revisions. I wanted to know if there is any standard type of video signal I could grab off of this thing or the internal video connector. I know I could take the external signal, but I didn't want to have to switch the video signal every time I turn it on, plus I haven't the clue if the switching actually works, because pressing Ctrl shift < or > doesn't do anything noticable like it does with my Compaq Portable I.
