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Thread: General TI-99/4A repair and maintenance questions

  1. #1

    Default General TI-99/4A repair and maintenance questions

    So, my TI-99 has been relatively fun, but it's been having some issues lately, and I'm looking to try and fix them. The biggest issue is the crashing. Every so often, usually on the first or second boot, the machine will go to a solid blue screen and hang. This is usually on the boot menu, but it has happened in a game/in BASIC. If a tone was playing, that'll hang too. What could be causing this? It's happened with a cartridge in and without. If it happened after running a while I'd assume it's overheating, but this is usually within the first couple of minutes of running it. I haven't taken the machine apart yet, so maybe the issue will be obvious, but knowing what to look for will help too.

    Another problem is the keyboard. It's a stackpole unit, and it has some pretty substantial key bounce. Can I reduce this in anyway? I have a Mitsumi keyboard from a broken unit that I've considered using instead. Is it better to type with compared to the stackpole switches? If I replace the stackpole model, what should I do to the Mitsumi (if anything) before installing it?

    And as a final question, what should I do to make sure the unit lasts a long time? Are there any problematic parts that can damage the system when they fail? Do any parts (other than the internal power supply) run hot?

    Thank you!
    Looking for: Tandy TRS-80 Model 100/101/102, Macintosh LC III/Performa 450, working Zenith Z-171 floppy drives

  2. #2


    Hi. You might have an overheating issue with one of the components. Most ICs and the power transistor will be warm to the touch. Almost any electronic component on the motherboard could be failing due to age. Caps and resistors will generally lose their rated value over time. If they get below a certain threshold, they will not be doing their job all the time. Dust and heat are the biggest enemies of electronics. Keep your system covered when not in use. You might also consider what I did back in the '80s. I socketed all the ICs on the motherboard. This allows you to replace a failed IC but simply popping it out and replacing it with a new one. It took a little bit of time to do but it's well worth it. De-soldering and soldering connections repeatedly will most likely cause them to break or lift off the motherboard. If you've ever seen the motherboard then you know how sturdy the TI is. The circuit traces are much thicker than computers nowadays and there's plenty of solder on them. They're like little mountain ranges.

  3. #3


    One other thing I thought of that I have learned about intermittent electronic problems is to check the solder side of the board for bad or broken solder joints. Inspect each joint with a magnifying glass and look for a black ring around the pin. This kind of problem can occur over time and can lead to the connection breaking contact intermittently.

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