I made a piggy-back affair to do the modification. IC 74LS27 has had pin 4, which ultimately goes to A2, bent out so it is no longer in contact with its socket or the board. An inverter, a 74LS04, has been piggy-backed onto the top, in a socket, with pins 7 and 14 for 0V and 5V soldered to the same pins on the 74LS27. Pin 4 of the inverter is used for the alternative A2 signal. All the other pins on the inverter are unconnected, so those pins have been bent outwards on the IC socket so that they do not make contact.

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