I did ask. Regarding the two shades of Grey, they are represented in memory by either A or 5 which in both cases turns into a 50% duty cycle square wave going to the video mixer (those three resistors on the right side of the board). Changing the duty cycle of the signal (percent hi versus low) will change the shade of grey, as well as affect other colors. Woz suggested that it could be done with a resistor, capacitor and diode, though he didn’t specify the exact circuit.

I did some experiments over the weekend and found I could easily get an effect just by adding a 47pF capacitor to the output of the 74LS74 at B10, pin 5 (rev 0 schematics). This gave slightly different shade of gray, but didn’t affect the other colors very much. However that capacitor and some other things I tried, really messes with the integrity of the signal, so I’m looking for a “cleaner” solution. Maybe I’ll try using a 74LS123 one shot, though it kind of violates Woz’s idea that it could be done without adding chips. Maybe the integrity of the signal doesn’t matter that much and the simple capacitor solution would be fine. You could use a variable cap and make the effect adjustable.

This flip flop is clocked by the system 14MHz clock, so you can’t do it with normal digital logic. Also, fooling with the clock input to that flip flop would likely upset timing for the entire system.

He didn’t say what he had in mind for eliminating a chip or two.

regards,
Mike W.