PAL color smearing problem - reloaded

[ferdimh@gmx.de]

There is a solution for the PAL color smearing problem on the apple //
e:
http://groups.google.de/group/comp.sys.apple2/browse_thread/thread/5bd5e38c50213764/ee606cc724870749?lnk=gst&q=pal+encoder+schematic#

I just installed it and noted a problem in the mixed mode (either Hi
or Lo-res):
The color on The top of the screen is messed up, and the TV is very
sensitive to the color subcarrier frequency. My oscilloscope showed me
that the Color burst is missing in the Text part and during part of
the retrace. This is somewhat logical, since the Linard's mod kills
the color subcarrier when the 3.58MHz trap is turned off. It would be
great to use a "TEXT" line (as it is available on the Apple ][/][+) to
kill the color, but it seems to be unavailable on the //e (I don't
have "Understanding the Apple //e" and it isn't online anymore...).
There is another possible fix:
One just needs to delay the turn-off so that the color burst will not
be killed in mixed mode, but will be in text mode.  I used the
following circuit:
Get 2 diodes (1N4148 or similar), 1 10µF cap and  a 22K resistor.
Connect the cathodes of both diodes and solder one anode to Pin 1 of
A13 (TCA650) and the other to Pin 9 of C15 (74LS74). Wire the resistor
and the cap from both cathodes to ground. If you use an electrolytic
cap, the cathodes are "+".

Pin 9 of C15 goes high when color is enabled. The cap is charged
through the diode if in graphics mode  and discharged through the
resistor. But draining the charge takes too long so that the cap is no
fully discharged in the short text period of a mixed screen.

But if has been no graphics for some time (~100ms), the cap will be
discharged and resistor and cap will load down pin1 of the TCA650,
which kills the color carrier like in Linard's mod.

I'm sorry I didn't post that on the old thread, but I was unable to
post there.

BTW, does anybody have "Understanding the Apple //e" ? I would really
like to have it but I can't find it anywhere.

-----
Ferdinand Meyer-Hermann