Casio fx-8500G weird behavior with FA-80 interface

[Dave Britten]

(05-03-2022 11:01 AM)blackjetrock Wrote:  Hmm, odd. Presumably this happens on both FA-80s?

The circuit for the FA-80 is here:

http://www.pisi.com.pl/piotr433/fa80.png

I don't see anything obvious that would cause this behaviour. You could try disconnecting some of the control signals on the connector and see if that affects the behaviour. Are all pins and sockets on the I/O connector on the calculator OK?

Andrew

Yeah, exact same behavior with both FA-80s, which work fine with the fx-8000G. I haven't done any extensive continuity testing and tracing to see if there are any dead-ends on the I/O connector pins, but I did reflow all the solder where the port connects to the board (which didn't change anything). It's super weird, it's like a good chunk of the RAM and ROM are just not there anymore, and as soon as you disconnect the interface, the calculator acts normal again.