[Coco] Need help with composite output for CoCo

[Zippster]

I haven’t had any problems on modern TV’s using 6847/1372 circuits designed to output NTSC
or transistor driven Luma (Y) from the 6847, not familiar with the CoCo1 circuit however.



- Ed


> On Feb 14, 2015, at 10:03 AM, Michael Rowen <mike at borncoco.com> wrote:
> 
> I agree that these circuits don't seem to be able to drive modern video inputs. I had the same experience you had - black screen. I had one old CRT monitor that would show up a very dim back on gray. I picked up an old CoCo 1 with a similar circuit in place, same result. Output looks OK on a scope, but not powerful enough to display on a modern LCD TV. The only circuits that seem to work without issue are those based on a an MC1372. I'm sure there are amp designs that work, but haven't been published or fully reverse engineered. There are cheap devices in the $14-$30 range that will convert RF out to VGA. Good Luck!
> 
> -Cheers,
> Mike
> 
> 
> 
> 
> 
> 
> 
> Jamie <reinsj at nbnet.nb.ca> 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
>> 
>> 
>> 
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