๐บ๐ธ Tandy Colour Computer 2: Part 1 (US NTSC model in Australia) [TCE #0526]
22About time I did some work on this fellow ... the Tandy Color Computer, or CoCo, 2. It came from the US ... I think there were just more available for sale there than in Australia, similar to the TI 99/4A for example. Not sure if I can add much value to the scene as there are many far superior YouTube channels with more interesting videos about these machines. But let's have a go anyway.
It's a model 26-3127B apparently with 64KBytes of RAM comprised of eight 8042665 chips. The motherboard is marked 20261058.
Relevant Patreon Post:
https://www.patreon.com/posts/tandy-coco2-113667495?utm_medium=clipboard_copy
00:00 ... Start
02:20 ... Opening it up
03:15 ... Original owner & purchase date?
04:20 ... Installed RAM?
06:00 ... RF modulator
07:50 ... Datasheet - converting to composite video output
12:10 ... Checking transformer output voltage
15:00 ... Removing the RF modulator can
18:00 ... Initial removal of components
22:04 ... RF modulator converted to baseband composite
23:15 ... We have composite video output ... just about
27:20 ... Comparing with ๐ด ๓ ง๓ ข๓ ท๓ ฌ๓ ณ๓ ฟ Dragon Data 32
29:50 ... And with the ๐ซ๐ท Thomson MO5 Platini
33:08 ... Channel outro
As it came from the US it expects 120VAC power and outputs NTSC via an RF modulator ... so two hurdles to overcome, hence why it's only just appearing now.
It uses the Motorola 6809 CPU, apparently one of the most advanced 8-bit CPUs at the time, but just too expensive compared to the 6502 and Z80, not to mention the appearance of the Intel 8088/8086 CPUs.
I'm thinking of replacing the iron-core transformer with a toroid ... the US transformer outputs about 8VAC under load and I have a toroidal transformer that will fit in the same space that outputs 9VAC ... close enough.
For the video output it's not possible to simply gut the RF modulator can and replace it with a simple capacitor (like in the Speccy) ... it uses an MC1372 chip which expects to be fed the parts of the colour video signal separately. But it is possible to modify the circuit so that the chip will output a composite signal ... requires some work though.
There are modern alternatives available that are probably much superior but they will take time to acquire.
For now, let's just fiddle with the composite video output.
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