Low cost 5101 Adapter
This Adapter is using a cheap PIC (which need to be programmed with the 'hex' file provided), a Diode and a capacitor, that's it!
The program use the internal RAM and EEPROM of the PIC. The capacitor and the Diode are necessary to give the PIC enough time to save the RAM Content to the EEPROM after switching of the pinball machine.
No backup battery needed anymore!
The Adapter does only work with Bally and Stern MPUs (in Bally compatibilty mode) produced between 1977 and 1985!
In case you do not have a PIC programmer I do recommend a PICKIT3. Please note that my own DIY PIC programmer cannot be used as the 5101 PIC needs to be programmed in HVP mode!
There is a jumper on the board which do clear the PIC memory. It is recommended to clear the memory once before you use the adapter on a new board.
In rare cases your board will not boot after inserting the adapter. Mostly this is because of a bad CPU clock caused by changed values over time of capacitors C14 & C15 and resistors R4 & R10 on the Bally MPU. While the 5101 runs the PIC need a more accurate clock. Original values are 470pF and 5,6KOhm. I recommend to change C14 & C15 to new ceramic 1nF caps and resistors R4 & R10 to low tolerance 2,7KOhm resistors.