To use the JLO 64K RAM board (from the TS1000) on the 2068, it is necessary to make the following changes:
1. Remove the feedthrough at pin 5 of U5 (74LS138).
2. Remove the feedthrough just above the edge trace that is furthest to the right on the component side of the board. (This is below and to the right of R3-2.7K Ohm.)
3. Remove the feedthrough just above and to the right of R1 (2.7KOhm), which is in the middle of the board. (This is the same feedthrough that is removed for using machine code above 48K and the Video upgrade.)
4. Remove the feedthrough above U5 and just to the right of the 48/64K legend. This is the ROM CS not trace.
5. If you are adding memory to the EXROM bank then skip step six and continue with seven.
6. For decoding in the ros (cartridge) bank and the use of the first 8K chunk (0 to 8K) is desired, then jumper pin 15 of U5 to the anode of diodes D3 to D6 with a 1N4148 diode. Connect the cathode of that diode to pin 15 of U5.
7. Set the Bank A/B switch to its OPEN state, 8 to 12K and 12 to 16K switches on and the 48 to 64K switch on.
8. Jumper pin 5 of U5 to either EXROM not (trace 27A – on the bottom of the 2068 expansion port) or the ROSCS not (trace 28A – the next one over on the expansion port of the 2068.