I have this 600XL with what seems to be an extra keyboard connector board that goes between the keyboard connector on the motherboard and the 600XL keyboard ribbon cable. Did anyone see that before and know what it is used for?. This particular 600XL does not have any upgrades other than the 64K Ram mod.
Here's a photo of the extra connector board:
The type of keyboard used is known as a "Low-resistance contact" keyboard, the resistance being about 1000 ohms or so. As you use the keyboard, the resistance of the contacts tend to go up as it wears and oxidizes.
For the regular keyboard and the RESET key this increase in resistance causes
no problems as of yet but time passes (decades) keys will begin to cease registering. But the console keys (OPTION, SELECT, and START) are read by a different IC, and the change in resistance will eventual