CoCo1 composite video(leadedsolder.com)

30 pointsby zdwletztes Jahr4 comments

https://www.leadedsolder.com/2025/07/15/tandy-trs80-coco-composite-mod-aquarius.html

4 comments

msarnoffletztes Jahr

Did this recently for my CoCo 2. Used a mashup of several composite mods floating around (including this one) and built it on a piece of stripboard that fit in the same footprint as the RF modulator. Sourcing the MC1372 was tricky, but NTE makes a replacement, NTE855. I used a 3.5mm TRS jack for the audio/video output so I didn’t have to drill a second hole in the case, and then all you need is a cheap 3.5mm stereo to RCA cable.

Wish I had a schematic but I kinda just wired it freehand.

kazinatorletztes Jahr

Looking at the monitor circuit with the two transistors, it's odd how the emitter is just connected to ground through only 122 ohms. Why would you have that 100 ohm resistor there?

Indeed, I found other versions of the circuit which don't have that:

https://www.cocopedia.com/wiki/index.php/CoCo_1_composite_vi...

alnwlsnletztes Jahr

Oh hey, I did this too. I'm pretty sure I tried OP's same circuit, but I wasn't happy with it.

https://alnwlsn.com/z/coco1-vid/coco1-vid.html

mikewarotletztes Jahr

The 2n2222 pair is a dual emitter follower, it is unity voltage gain, but does remove some of the bias from the signal.