I have been selling ROM adapters for the Commodore PET-2001 since 2009. Over these last five years I have been honing my design skills on my many different replacement electronic parts and through that process I have realized that my adapters are much in need of an update, so here it is. This new generation of ROM has many improvements including:
-A 74HCT138 decoder IC instead of the primitive diode-transistor logic used in the first version. This means a more reliable replacement that more accuratly mimics the original MPS6540.
-The clock signal is now wired as an additional ‘chip-select’ line to more closly mimic the behavior of the original MPS6540.
-Batten and Allen PCB edge pins instead of round wire pins. The old adapters would only work reliably in one of the two types of DIP socket used in the original PET. These new pins exactly replicate the shape of a proper DIP pin and thus will work reliably in any DIP socket without damage. No kind of through-hole pin can claim this!
-An overall lighter weight and shorter design. This means that that part will be less likely to come loose from the socket if the PET is jarred.