[sdiy] Buffered/unbuffered CMOS in Oberheim logic boards

[g m montalbano]

Hello-
I'm currently trying to repair a severely damaged Oberheim 4-Voice.
The keyboard module (an overhead board and two channel boards)
contains several dozen CMOS chips, most of them series A (or U).
I recall reading years ago someone (Kevin Lightner?  Scott Metzger?)
posting that it is necessary to use unbuffered parts when replacing
non-functional chips on these boards.

Is this true?  This period of Oberheim was known for some baroque
logic circuits (see the memory board for the OB-1 for a good example),
and I have no idea if there's a way around using these increasingly
rare (and hellishly expensive) parts.

Thanks.

~GMM