Commodore 64 repair.... New SID Arrived.

Assuming the SID is OK, It's most certainly the PLA, could be the 139 but I don't think so. Having said that, the point you get keyboard problems would point towards a CIA fault, but... The 74LS139 provides the chip selects there for the CIAs too I think. I would piggyback the 74LS139 with another chip (not soldered on, just grip the chip underneath) and see if it makes any difference. Beyond that I would swap the PLA, but you may also have a CIA fault affecting the keyboard. Try the 139 first since its cheap.