Before
Toggle jumper JA1 to change DS1 to DS0, cut the trace going to pin 34 on the data connector.
Solder a wire from pin 2 of the data connector to the trace that used to go to pin 34, on the other side of the cut (or directly to the leg of the FDN303 chip if you have the skills/tools), solder a wire from pin 34 of the data connector to the test point TP15.
User ceetee mentioned that you might have to remove the short circuit block from JA2 for it to work properly as df0:
Here are the modified areas circled.
Researched by Anssi Luukkonen