Take a note of the pin connections
Ensure there is no disc in the machine, remove the parallel port cover on the back, flip your machine over and
remove the 6 retaining screws.
Flip your machine back the right way and lift off the top cover, remove the drive unit by gently pulling out the
ribbon cable and the small motor supply plug, lift the drive unit clear and set it in a safe place. Remove the
cable restraint and disconnect the second ribbon cable and the main power supply cable.
Remove the four phillips screws holding the plate and lift it clear, you might have to wiggle it a bit as it tends
to hang on the locating pins.
Remove the four phillips screws holding the system board in place and lift the board clear.
The steel screening plate will have to be desoldered and removed for access to some of the solder points, some
people like to bend it back but this deforms the plate, you may need a heavy soldering iron for this job as
the solder points are quite large.
This is the system board removed and the metal screening removed for access.
This is where to put the mod-chip on this model, there's plenty
of room and it will stay cool under the mother board, you can use a glue gun or double sided tape to secure the mod-chip, small pieces of tape keep the wires from moving around on the top side, the wires are threaded through a conveniently placed spare
hole.
And here are the solder points! 