[SiriusHardware]

I'm afraid all three of those buffers are soldered in place. If UA7 / 8 were socketed then, assuming the buffers are at fault, swapping them would move the fault to bits 3 and 4.

In an earlier PET thread we also eventually ran into problems with these buffers and the OP in that case ordered a set of replacements from somewhere in Europe - but although described as MC3446s the small print said they were actually something else which was an equivalent. Unfortunately I didn't remember to note down what that was but I have asked the OP (who has been back here recently) if he would kindly read the numbers off the chips he received, as they did fix his IEEE port problem.