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Thread: Toshiba T6400DXC- Normal LCD Operation for 1992?

  1. #1

    Default Toshiba T6400DXC- Normal LCD Operation for 1992?

    I came across a non-responsive Toshiba T6400DXC on eBay last week for my birthday in hopes that I would be able to transplant it's screen into my T3200SXC. No such luck. It was too big.

    So I did the next best thing, and decided to try repairing this computer, since the power supply worked and the fans were running whenever I turned it on when plugged in. Wouldn't you know it, it was capacitor plague; the exact same kind of capacitor that was used in my Sega Game Gear. Thankfully I had gotten to replacing the capacitors early, and the worst of the leaks were some light corrosion on nearby solder points.

    After that, I was able to get a beep out of the system, but still no internal video or hard drive. That is, until I plugged in an external monitor, both the internal screen and the hard drive activated. My guess is that the other capacitors in the system needed to be exercised, since they had both not been used in such a long time. The screen displays fine, except it shows a strange pattern. It does not display a consistent version of the light-grey text that is normal for MS-DOS. Instead, the text looks more like a modern-day LED three-color lamp, or a composite color video signal from an Apple II or CGA RGB output. I understand the text in the attached pictures looks normal, but the zoomed-out picture was unavoidably blurred by my smartphone's camera.

    I'm not familiar with TFT LCD screens from this era of computing, because my family never owned a laptop/portable computer until 1997, and by that point, the TFT tech had advanced to a much more detailed resolution. Looking at the LCD screen up close shows that the subpixels seem to be displaying somewhat normally.

    That being said, I really don't know if the color displaying like this is normal for a TFT LCD from 1992.
    Attached Images Attached Images
    Last edited by T-Squared; August 13th, 2017 at 04:33 AM.

  2. #2

    Default

    I'm not 100% sure I understand what you're describing, but I think it's normal for a 640x480 screen. It just has bigger pixels, so it's easier to see the individual color cells (which I think is what you're describing).

    Here's a picture of my Toshiba 400CDT screen for comparison (a TFT active matrix 10" 640x480):

    IMG_20170813_065215.jpg

  3. #3

    Default

    Quote Originally Posted by jmetal88 View Post
    I'm not 100% sure I understand what you're describing, but I think it's normal for a 640x480 screen. It just has bigger pixels, so it's easier to see the individual color cells (which I think is what you're describing).
    Basically, what I am seeing on the LCD is color fringes in the pixels of the text, much like you see in an Apple II when it's connected to a color TV, or when CGA is output to a color monitor. It can be seen even when viewed from normal viewing range.

    I was able to put together an imitation of what I see. (Hopefully the forum's jpeg compression doesn't wreck it. Which it did... as well as resized it.) If I had to guess, the reason why it looks this way is because it's more primitive, and also because of the bigger pixels, as you had said.
    Attached Images Attached Images

  4. #4

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    Quote Originally Posted by T-Squared View Post
    Basically, what I am seeing on the LCD is color fringes in the pixels of the text, much like you see in an Apple II when it's connected to a color TV, or when CGA is output to a color monitor. It can be seen even when viewed from normal viewing range.

    I was able to put together an imitation of what I see. (Hopefully the forum's jpeg compression doesn't wreck it. Which it did... as well as resized it.) If I had to guess, the reason why it looks this way is because it's more primitive, and also because of the bigger pixels, as you had said.
    Yeah, if you look at my picture there's a red fringe on the left and a blue fringe on the right, so I'm pretty sure what you're seeing is just that same property of the LCD.

  5. #5

    Default

    Here's a better representation of what I see. (Finally, the forum didn't mangle the quality.)

    When I saw it, I thought it was a glitch at first, like the pixels were not matching up exactly one-to-one on the screen.

    EDIT: By pure happenstance again, the machine booted up. It seems the screen is just fine (It shows color nicely), if a bit flickery due to the refresh rate.
    Attached Images Attached Images
    Last edited by T-Squared; August 14th, 2017 at 11:10 AM.

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