I'm hoping someone can help me with the weird behaviour of the below clone 80 Column card on my Apple II+. This card has onboard switching, and a pass through for the composite output of the Apple II motherboard. But when I enter the command PR#3, the cursor disappears, but the output doesn't switch. Clearly the 80 column card is working, because the beeps become a lower tone and if I press "CTRL-Z,1,RETURN" the cursor returns to the 40 column screen.While in hidden 80 Column mode, if I type PR#6 to run a program from the floppy drive (I'm typing to the 80 column screen that I can't see) when the program starts the card then switches to 80 column mode even though the software is running on the now hidden 40 column screen.
It seems like the screen switching is backward to the way it's supposed to work. I've tested every IC on the 80 column card using my Minipro programmer, and I've tried swapping out the graphics chip for a new unit, so I feel like the problem might be with the Apple II+ motherboard. Does anyone know how the switching signal gets to the card so I can look for a problem on the motherboard? Obviously it comes through the 50pin edge connector, but what signal is used?