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Re: Multinorm TV woes - no NTSC color display



Michael J. Mahon wrote:
Linards Ticmanis wrote:

David Wilson schrieb:


But my computer is a II+, not a IIe. What is the difference between NTSC II+ motherboard and PAL II+ motherboard beyond the jumpers and the quartz?


Apart from the jumpers and the main oscillator frequency, nothing.
Making the changes you have done should return the board to NTSC
functionality. Have you tried tweaking the Color Tone variable
capacitor (C3)?



Hello David,

Yes, I did. Didn't produce any visible change whatever. That capacitor
modifies the color burst phase, not the phase of the visible picture
itself, right?


That's right.  And it doesn't modify the *frequency* at all, so
it would not affect detection of the color burst.

I see two possibilities--1) the 14MHz crystal you installed is just
enough out of tolerance that the monitor does not recognize the burst
as a color burst, or 2) the monitor is applying some strict criterion
to the video signal that the Apple does not conform to.  (This is more
of a problem with monitors that use digital decoding.)
Actually thinking of 2) I tried another frame grabber, actually a video grabber with the NTSC IIe output and it even failed to sync. With the old frame grabber, I have, it works well...

BTW I got another CGA monitor (off eBay and I had to repair it, broken powersupply) and now found that it needs the VSYNC signal to be a real VSYNC not only a copy of CSYNC (Which is how it works with the IBM CGA monitor). This monitor is a CGA/EGA monitor from Shuntex (SHX). Sometime, not soon, I will try to use it with the IIe in analog mode to get real Apple NTSC colors :-)

--
Knut
(delete 'nogarbage.' for email)