Composite output

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Jul 6 16:11:28 1997

In message <199707061451.JAA22190_at_challenge.sunflower.com> classiccmp_at_u.washington.edu writes:
> Once I try it myself, sure. All I planned on doing was desoldering, or
> patching onto the input of the RF modulator, {the 1.5x2in box that you plug
> your tv into) to a composite RCA style connector. Hoping this will work.

That's what I did (in most cases).

The modulator typically has 3-5 connections. They are :
Ground (connected to the 0v line of the computer)
Power (typically +9V - +12V)
Video Input (Composite - jsut what you want)

Channel Select (in the US - connected to the Channel 3/Channel 4 switch)
Audio Input

Most modulators are standard parts, and you can get data on them (or at least
a pinout. I'm unlikely to be much help here, since I'm in the UK, and our TV
system is different).

Anyway, you need to identify the video input. Either look at the modulator
data sheet, the schematics of the computer or trace it out by hand (eliminate
the ground and power pins, and look at what's left).

I've just found the (USA) CoCo Technical manual. The modulator has 5
connections, including the case. It's a UM1285-8 (I suspect that this is used
in other computers as well). Anyway, the connections are :
Case - ground
1 (Nearest the RCA socket on the modulator) - Video Input
2 +12V power
3 Audio Input
4 Channel Select

Now connect a piece of 75 Ohm video cable with the centre wire to the video
input pin on the modulator and the braid to the 0V line. Connect the other end
of that cable to the monitor.

-tony
Received on Sun Jul 06 1997 - 16:11:28 BST