The photos aren't that clear but I can tell that you have mostly 5 volt supply, hex Schmitt-Trigger inverters, caps, and resistor packs on that board. Just what you would expect to see on a board that accepts and debounces inputs from the outside world. RC networks with zeners or transorbs would be used to protect the very high impedance inputs of the CMOS ICs. The "HC" family of CMOS devices were designed to use the same pin outs and 5V power supplies as the older 7400 and 74LS00 families. If my suspicions are correct, your circuit would work with the zeners or transorbs removed IF other components aren't defective. In that case, a P6KE6.8A or 1.5KE6.8A would be your commonly available replacement part. All of the other parts on that board should also be available from Digi-Key, Newark, Mouser, Allied, Etc.
Joe
