[Coco] Need help with composite output for CoCo

[Gene Heskett]

On Saturday, February 14, 2015 08:37:14 AM Jamie wrote:
> Hi All,
> 
> So I'm trying to build a composite video converter for a coco 1 and I
> can't seem to get it to work. I started with a simple design from Hot
> CoCo which uses a couple of transistors and a few resistors and then
> tried Dennis' TV Buff.
> My question is, should the output work on a modern flat screen LCD TV
> or do monitors with composite input work differently?  The TV screen
> responds by going black but I'm not getting any picture at all.
> 
> Thanks!
> 
> Jamie

You probably need to look at it with an oscilloscope to verify that you 
have good outout.

Its also possible that the modern flat screen with a composite input is 
expecting an ntsc spec sync signal, and that is somethng the coco's have 
never generated.  In analog days, the tv's didn't care that much, so what 
the coco outputs was reasonably close and acceptable, with a wee bit of 
trees waving in the wind at the top of the screen.  I have some older 
Samsung flat screens that aren't entirely happy with the output of an 
older s-vhs machine and will blink black for a few milliseconds if the 
tracking isn't pretty dead on.  Its happier with an old dvd feeding it.

Cheers, Gene Heskett
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