Identifying IC chips that have been sanded down?

[jimosity]

I have a couple units that I want to RE and a couple IC chips have been sanded down to avoid this sort of thing.
What options are there for figuring this sort of thing out?

[theehman]

Which units are they?  Someone may have already done the work.

[earthtonesaudio]

An educated guess is the fastest way to figure it out.  Part of that guesswork includes the assumption that if the part is sanded down or disguised like that, it's probably not anything out of the ordinary.  Next would be: identify power pins, determine the pinout based on the function of the circuit.  Possibly scope probe the chip in-situ with a function generator to see what's going on.  If it's a common pinout (dual op-amp perhaps) and you really want to figure out what it is, it gets exponentially more difficult.  You can remove the chip and test it's parameters (bandwidth, gain, CMRR, PSRR, input resistance, etc), but in my opinion that's too much work.

Which units are they?  Someone may have already done the work.

Yep, or that. 

[Mark Hammer]

Seeing where the power lines go and identifying inputs and outputs is often a useful step, however it would not be able to tell you, for example which 8-pin dual op-amp is being used, only that it was an 8-pin dual op-amp.  On the other hand, often that is sufficient information to produce a reasonable replica.

[jimosity]

Both are Axess Electronics units.  One is a GRX-4 and the other is a BS-2.