[Coco] Run of RGB2VGA boards

[Barry Nelson]

Your are correct, pin 10 of the RGB connector is wired to a 4.7k ohm resistor to +5V and another 4.7k ohm resistor which is connected to pin 13 (PB3) of U4, a 68B21 chip. I wonder what it was used for, and if it was used… It does look like it an input that would be normally high unless it pulled low externally. It shows up in my CoCo 3 schematic but I have little information on it other than how it is wired. Does anyone know any more about this?

+————-------+
| 1 3 5 7 9 |
| 2 4   8 10|
+————------–+

Pin Name  Description
1   GND   Ground
2   GND   Ground
3   R     Red
4   G     Green
5   B     Blue
6   KEY   No Pin
7   AUDIO Audio
8   HSYNC Horizontal Sync
9   VSYNC Vertical Sync
10  ----- UNKNOWN input connected to U4 pin 13 (PB3)

 
> Brett Gordon beretta42 at gmail.com 
> Sat Sep 12 06:22:58 EDT 2015
> I think pin 10 is pulled high and stuck in one of the pia chips.  Ill check
> the schematics when i get to a real computer, tomorrow.