I've now measured RP1 and RP2 on a Lisa 2/10 motherboard --- I expect the values should be similar for a 2/5 motherboard.
The resistor packs are 20-pin DIPs. Oriented vertically, call the top-left corner Pin 1. Using a conventional DIP numbering scheme:
- Pins 1, 10, 11, and 20 are all shorted together
All remaining pins appear to be connected straight across the package with 50 ohms of resistance. So:
- Pin 2 to Pin 19: 50 ohms
- Pin 3 to Pin 18: 50 ohms
- Pin 4 to Pin 17: 50 ohms
And so on to
- Pin 9 to Pin 12: 50 ohms
Note that this arrangement is symmetric in all axes, so it doesn't matter if you get the resistor pack the wrong way round and put "Pin 11" up at the top left.