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Thread: TI 99/4A Video Display Issue

  1. #1

    Default TI 99/4A Video Display Issue

    Good evening gentlemen,

    I recently had the pleasure of purchasing a 1981 TI 99/4A. I have tried plugging it in to my television with a 5 pin DIN to composite cable that I usually use with my commodore 64 and received a somewhat readable but very distorted black and white image. I ran some software and it all seemed to run properly. It should also be noted that plugging the DIN to composite cable into a television will yield a different result than plugging it in to a USB capture card. The capture card will yield a completely unreadable image of red, blue, and green scanning lines.

    I decided to open up the TI and noticed that there was white goop caked onto one of the chips. I assume that this isn't correct and that may be the issue, and thus needs to be cleaned, so I supposed the next question would be how to clean it?

    Assuming the goop is not the issue, what could be?

    advanced computing.jpg

  2. #2


    It looks like a heat sink was previously attached to the top of that IC and what you are seeing there is the usual white thermal coupling grease. If that is the case, then the IC could possibly run too hot without the heatsink attached. It would pay to measure its temperature when running, just in case a heat sink needs to be fitted.This issue may not be related to your current problems.

  3. #3
    Join Date
    Jan 2013
    Marietta, GA


    The heat sink is usually built on to the metal RF shield that surrounds the motherboard. The white goop is thermal paste, and is normally supposed to be there. It looks like yours is missing the RF shield?

    That chip does not overheat when left in the open, but inside the tight RF shield, heat becomes an issue.

    I'd double check the wiring and the DIN socket, but TI-99/4As did not always put out the most stable composite video signals. Just be glad you are not trying to use an RF modulator with that.

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