For a more professional description look at Roine Stenberg's JagServer website.
Attention: This is on your own risk!
Don't blame me if anything goes wrong!
If you're not experienced in soldering, stop here!
You need: - a reset-key
- two wires (marked with yellow in the pictures below)
1) Open your Jaguar console and remove the shield. Localize the Boot-ROM, it's near the power-plugin.
2) Solder one wire to pin 16 of the BOOT-ROM (U35), connect the other
end of the wire to the reset-key.
3) Solder the second wire to pin 13 of U9 (this is a SMT-device, so be
carefull!) and then connect it to the reset-key.
U9 is at the opposite "corner" of the PCB.
4) Now drill a hole for the switch into the console cover near to the
power plug and place the reset-key there.
Here is a picture of a Jaguar with a reset key (the red one) and a BJL-ROM-switch:
Here is an overview-picture of a Jaguar with reset-key and BJL-ROM and