I have an 820-0026-C keyboard encoder board attached to a pre-RFI Datanetics keyboard. Its being used with a rev 4 motherboard (II/II+).
The encoder board seems to match the schematic in Fig 7.8 of "Understanding the Apple II". The encoder IC seems to have an apple part # 331-0931-B, and manufacturer part # SMC KR3600-070 (instead of the AY-5-3600 in the schematic).
Unfortunately, it seems as though the keyboard encoder IC is faulty - some of the encoder IC's data output lines are floating at 1.65V instead of outputting the (inverted) key code.
I haven't desoldered the 74LS04 inverter to test independently, so for now, I'm assuming its the encoder itself that is at fault... I thought I'd check here first, before taking a soldering iron to the board...
There seem to be several KR3600-XXX flavors 'out there', but so far, I've failed to locate any datasheets that contain the key coding matrix of any of the variations. I was hoping I could find a more commonly available variation that might also successfully decode the apple key matrix.
Does anyone have such a datasheet - eg, that might allow me to identify other KR3600-XXX or KR9600-XXX variants that might decode the keyboard correctly, or already happen to know of variants that will work?
I'd also be interested in the same type of information for compatible AY-5-3600-XXX, or any other known compatible encoder ICs...
I'd appreciate any info you might be able to share - I'm a newbie at apple ii repair, but I would like to get this machine operational again, for old times sake.