Change it
Hi!
Maybe the best thing would be to change the PLC.... after all, next time something happens, you were the last one to touch it!!! So if you are going to support them, it has to be on something you know, right?
However, the F1/2 series are pretty straight forward to program (mitsu-style). The major difference from Fx (newer) is different "name areas" on IO, timers, STL, etc.
If you know mitsubishi, you know F2 also!
If you want to change the PLC, you can open the original program in Medoc, and select "change PLC" and the program will be converted to a selected PLC type. The only thing is that you have to define if there is a mismatch in old vs new instructions, names on devices etc. If it is basic logic, you shouldn't have any problem.
When it comes to the EEPROM, when inserted in the PLC, the EEPROM just replaces the PLC memory. So if the EEPROM is inserted, you will work on that memory when you're programming with the computer (remember to turn off writeprotect (dipswitch))!
When you're using a new computer to program the old plc's, you should set a timeout in MEDOC (to not get com-errors while downloading). This is done by writing "T" and timeout-time in seconds after the MEDOC.EXE command to start Medoc.
Example, timeout 5 sec: "C:\MEDOC\MEDOC.EXE T5"
Hope this helped!
And have some faith in those old plc's! They are ok when you get to know them!
Support (spares) will soon be a serious problem regarding these things...... You have to go to the museum to get parts!