Working on a Super Rare TI-99/4

The TI-99/4A is a really cool machine with a pretty terrible design, but you know what would make it even better? If it was way worse! The TI-99/4 is what predated the 99/4A and it’s an incredibly rare machine, with only around 20,000 units built. The 99/4A get’s the “A” in its name from the TMS9918A Video Display Processor, or VDP. But, the 99/4 uses a TMS9918 (no A), which is why it doesn’t have an A in it’s name. The 9918 is much worse though, lacking a bitmap mode. Throw in the weird chiclet keyboard, and the 99/4 is worse in everyway, except for rareness and coolness. And I love rare and cool. So, let’s see if we can get this machine going!
(Spoiler alert, we don’t…)

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Intro Music adapted from:
Artist: The Runaway Five
Title: The Shinra Shuffle
https://ocremix.org/remix/OCR01847

Thanks for watching!

Chapters
0:00 It’s good to be back
1:17 Introduction
4:11 TI-99/4 vs. TI-99/4A exterior
6:25 Disassembly
7:53 TI-99/4 vs. TI-99/4A interior
10:10 Cleaning
11:35 We’re gonna need a monitor
12:54 Monitor disassembly and cleaning
13:53 First test
16:06 Troubleshooting begins
16:45 A bad video circuit
19:40 A bad 74LS138?
21:35 A bad 4116 RAM chip
24:45 We’re getting there, just not there yet
26:10 Bunny!