Hi Tom. Eric is right, the CPU is a somewhat primitve two chip
chipset.
I would suggest that you consider sending me your calc for repair.
Unless the calc has been subjected to "abuse", disassembly and
fiddling with the electronics, the actual devices are fine and it's an interconnect or cracked board problem.
I am pretty seasoned at digital (and analogue) electronics repairs.
I built my first "computer" from chips according to my own design
in 1984, so I know what I am doing ;-)
I worked for Canon Auistralia in my first full-time job in 1985,
repairing calculators (all kinds!) and desk-top computers.
If you want me to repair your machine, please write to me at:
donwallace63@yahoo.com.au
stating in as much detail as possible what is wrong (won't turn on, strange display, crashes when running a program, bad keys, etc...)
and how it got that way (got wet, dropped, on charger without
battery pack inserted or battery leaked, etc...)
Only trying to help.
Best wishes,
Don Wallace