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David Vella's Blog - Fixing My TI 99 4A


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In my Teens I was the lucky owner of a Beige TI 99/4A which my parents bought me for Christmas (1984). I was thrilled with it and in a few weeks I was writing small games and sharing these with my friends. My Software Developer Career started on that day.

31 years later exactly 6 months ago I joined the local Vintage Computer club and 2 months ago I told them that I would start displaying my TI 99/4A in the shows we do in schools etc... I tried switching it on again but to my dismay a long Tone and a black screen came up on the CRT TV.

I started looking for solutions on the Internet and happened to hit ATARIAGE, it was like a miracle for me, I could not believe that so many interesting people would congregate onto one forum.

From the tips I was getting I started the journey to fix my TI.
I started by checking the voltages of my power supply and found that the 8.5v AC was not coming out correctly, only 2.5V.

I took the transformer for new copper winding in a factory we have locally and the TI 99/4a booted up properly. The problem was that it only lasted 1 hour and I had the Long Tone and Black screen again. Now all the voltages were correct but TI was still not working.

I wanted to be bolder and fire up my trusty soldering iron and hand de-soldering tool (2 euro pump). I read that in many cases it is either the Video Chip (TMS9929A) or the VDP RAM (4116). So I purchased a new video chip. Replaced my chip with the new one but to no avail.

Then I ordered 8 VDP RAM chips, which are still on the way. I will socket all the chips so that I can replace the RAM chips easily if need be.

Today the 6th of December 2015, I started the de-soldering process and will keep this blog updated with the progress. The VDP RAM is difficult to remove as the solder is double sided and the two white strips interfere with the process of pulling the chips. I really would have finished this in an hour if these were not so in the way, but patiently today I removed 5 chips. More on this soon. :)

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http://atariage.com/forums/blog/628/entry-12531-fixing-my-ti-99-4a/
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