Re: Problem 2: no color -Re: Vertical Sync Issues with modern TV

[mjmahon@aol.com (Michael J. Mahon)]

Mike Willegal wrote:

>   Those old boards were designed to work as PAL or NTSC.  Cut a couple 
>of traces and add some blobs of solder to convert.  Didn't notice the 
>difference until I compared it to a "working" NTSC board. 
>
>   New Problem:
> I've changed the  board back to NTSC, but now I don't get any color.   
>Tried two different TVs and an RF modulator.  My other board of the same 
>vintage also doesn't exhibit any sign of color, either, though it never 
>had the issue with PAL sync timing.   I do get shades of grey.
>   
>   I don't believe it showed color before I made the changes to NTSC, 
>but am not positive, since my focus was on vertical sync problem and the 
>monitor I usually use is only monichome.
>
>   Any ideas on this one, before I borrow the Oscilliscope, once again.

The color subcarrier frequency of PAL is slightly different from the
NTSC frequency.  You will need to change the crystal in the clock
oscillator circuit to a 14.318MHz crystal to get NTSC color.

When you do get color, you will probably find it necessary to
adjust the color burst phase trimmer capacitor on the board
(assuming that it has one) to get correct colors.

-michael

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