Re: Analog NTSC to RGB converter?

[nyder <nyder.23@gmail.com>]

On Friday, November 2, 2012 3:01:01 AM UTC-7, Linards Ticmanis wrote:
> On 10/30/2012 01:27 AM, Alex Freed wrote:
> 
> 
> 
> > I only want to add that some 30 years ago I had an Apple connected to a 
> 
> > TV and discovered that the color saturation was way too high. Not a big 
> 
> > surprise: consider a 01010101... pattern. It is a 3.58 MHz square wave 
> 
> > rail to rail. The first harmonic of that is about 63% of that - a lot 
> 
> > more than the normal chroma signal. So I added a shallow notch filter - 
> 
> > a low Q LC tank in series with the signal and it actually looked better. 
> 
> > That's an LC tuned to 3.58 and shunted with a resistor. I definitely 
> 
> > don't remember the values after all these years :) If the colors are 
> 
> > oversaturated you may want to give it a try.
> 
> 
> 
> Thanks for the hint, but the 1084 has a fairly standards-conforming
> 
> saturation when the knob is in the middle position, which means it's
> 
> lower than on most TV sets (which tend to be over-saturated from the
> 
> factory, since - as I've read somewhere - this supposedly boosts sales
> 
> in the showroom). So even with the Apple II the colors are not all that
> 
> garish, and with a C64 connected they're even somewhat dull.
> 
> 
> 
> One more chapter to the saga: I didn't notice until a bit later that
> 
> when the multi-standard decoder chip can't detect any color encoding at
> 
> all - such as when an Apple II in text mode is connected - it will
> 
> continuously cycle through its four color systems while trying to find a
> 
> subcarrier. That means that the NTSC output line gets activated for
> 
> short time about twice per second, resulting in an ugly "pulsing" effect
> 
> of the external LC filter, with short drops in sharpness. I solved it
> 
> with a large capacitor and two resistors, now the NTSC setting of the
> 
> filter doesn't kick in until the NTSC output pin is stable at high level
> 
> for about one seconds.
> 
> 
> 
> Also I had a rather unpleasant fight with "Hanover Bars" in orange or
> 
> greenish-blue screen areas in PAL modem (around the U = -V points).
> 
> Correctly adjusting the PAL delay line is quite tricky in this monitor
> 
> as the setting doesn't seem to be entirely stable. I got it into a state
> 
> where at least at standard saturation the bars are no longer visible.
> 
> 
> 
> -- 
> 
> Linards Ticmanis

The Commodore 520 Adaptor has the circuitry to display pal or ntsc, might be easy/cheap to make an apple to amiga adaptor for it.   It's made for use with TV's and composite monitors.  Only thing that sucks is the weird 21pin plugs amiga use.   Thought I had one, was going to open it up and take pics of it's pcb, but it seems I don't.   Not surprised though, I manage to keep 3 commodore monitors (1902, 1080, 1084) and a Sony EGA Monitor (CPD-1302) over the years.

Anyways, those adaptors used to be pretty cheap, quick check on ebay put one at $40ish USD, but maybe you can find one there in germany pretty cheap.  Probably can hack a s-video single out of it.