BeebMaster - BBC Model B Disc Upgrade

Fitting a
disc upgrade

Depending on the motherboard issue number, there are some minor modifications to do here.

On the issue 1 and issue 2, the two pads of link S8 must be connected together with a wire link. For later issues, this link is already made with a track.

On issues 1, 2 and 3, cut pin 9 of IC 27 (the most south-easterly pin) as close to the PCB as possible. Cut the track which goes from pin 9 to IC 89. Solder a short length of insulated wire from the cut pin 9 of IC 27 to the East pad (ie. the right-most pad when looking at the BBC from the keyboard to the back of the computer) of link S9.

If you have an issue 4 or issue 7, cut the link at S9. Use professional wire cutters or an extremely sharp knife or pair of fine scissors. If you try to do this with something unsuitable, you will end up hacking away at the link for hours and could risk damaging your entire Beeb.