Unfortunately this beautiful TNC is not well documented (at least not as his brother PK-232). I’ve been able to acquire the complete manual with schematics (albeit something does not add up) and with some tinkering I discovered the use of most of the undocumented jumpers on the boards.
- JPA1, JPA2: bypass LP filters
- R166, R164: used to have 0V on PIN 20 of U41, U39
- JP11, JP12: bypass compressor
- JPT1, JPT2, JPR1, JPR2: jumper on (jumper off if you have DSP-1232, K1 must be installed too)
- JP1, JP2 on the daughter board: mystery