As I see it Erik and Rob are quite right. You should note Erik was talking in general terms. For young designers, it is important to learn from others about what to look for, and where tolerances in any design ( And as an instrument design engineer, this applies to mechanical systems especially) add up.

As I have no experience of mal-functioning 8052 swaps, I cannot comment from there, but I have a lot of experience with A/D and D/A 16 bit and above converters and can point out just about any of the major manufacturers, with the possible exception of Analog devices, who take great liberties with their specs for such things. Caveat Designer !

Steve