Rob Jones writes ...
> 
> Although the ][+ is already a great machine, is there anything that
> can be done to make it better? I have added an SSC card, 16K RamCard
> for a total of 64K, and another floppy drive (2). I am planning on
> making and adding the Hard Disk (IDE) card. The 6502 is a good
> processor, so that will not need to be changed, but Video leaves much
> to be desired: I am looking into a way of tapping the video area of
> memory ($0400~$0C00, $2000~$8000) and with a controller of some sort,
> make HGR / HGR2 display proper colours (without the fringes), as well
> as permanent 80-column capability.
> 
 ....

     I do not know how hard it might be to modify the hires display to
eliminate bleeding. Since most game displays are designed to work around the
problem, fixing it probably would not result in much improvement in showing
current games.

     The kind of fringing you get when displaying stuff like white figures
and Text in hires is built-in by the way color is encoded. A single ON
pixel-- one that is not next to another ON pixel-- is going to have color.

     You have the same problem when displaying Text mode Text in the area
beneath a hires or lores screen because color is still turned ON. However,
since you know you want all 4 lines of Text in that area to be in B/W, you
can get rid of fringing there by turning OFF color during that time.

     The catch is that there seems to be no way for the Apple II to turn OFF
color in mid-screen. It looks like once a composite color monitor gets the
Color Burst signal, color is ON for the entire frame.

     The way we finally forced B/W in the Text area was to run a line from
the Apple II to our Amdek Color-1 and just clamp the Color control during
Text displays:

The Text/GR signal from pin 12 of the 74LS02 at B13 goes via a 220 Ohm
resistor to a small NPN transistor (Base lead). The Collector goes via a 300
OHM resistor to +5V. The transistor output is from the Emitter.

The output gets sent via a line which runs to the monitor to drive an MTC-2
opto coupler chip (to the LED Anode). The LED Cathode lead goes to Ground at
the Video Input connector.

On the output side of the opto-coupler the Collector lead connects via a 300
Ohm resistor to the center wiper of the Color control; and, the Emitter lead
goes to the Ground end of the control.

     So, whenever the Text/GR signal is high (Text), the LED in the
opto-coupler turns ON and the optocoupler transistor conducts which
immediately 'turns down' the monitor Color control.

     It's a pretty easy mod which gets rid of the 'multi-color' Text shown
beneath many game screens.

     

Rubywand