8-bit Computer TV Channel Use

[tony duell]

> Yes, video is tricky.  I've just had an experience which emphasizes the
> topic under discussion.

The main problems stem from the fact that these computers output anything
but broadcast-standard video. In some cases it was because they were built
to a price and it was 'what can we get away with'. In others it was more a case
of getting extra features (like colour) almost for free.

> Just recently I got hold of an Amstrad CPC 464.
> http://www.classic-computers.org.nz/collection/amstradcpc464.htm

Incidentally, one of the better things (for me) about Amstrad machines 
is that service manuals existed for them. Said manuals are essentially
a schematic and a parts list, but that is all that is normally needed. Certainly
for the older machines (all the CPCs and PCWs and the earlier PCs) they are
not just boardswapper guides.

> It didn't come with its screen though (dedicated screens were sold with the
> machine). However British enthusiasts had developed an RGB to SCART cable

What are you doing for the PSU (the computer ran off the SMPSU in the monitor
IIRC)?

> for this very problem. Problem for me was that although SCART is a common
> video interface in Europe, it's rare in New Zealand. However I noted there

One problem with SCART (and I don't think it's the cause of your problems) is that
it is several interfaces on one connector. In particular there is composite video,
RGB video (using the composite pin for sync) and later S-video (using the 
composite pin for Y and IIRC the 'red' pin for C). Not all devices implement all
parts of the interface. In particular UK TVs almost always have the RGB inputs, 
VCRs did not.

The CPC output is RGB video, and AFAIK the CPC-SCART cable is a simple cable
with perhaps level-shifting resistors inside. So it will use the RGB pins on the 
SCART connector. 

-tony