Hi Roger,
You did not give the correct schematics! All the ICs are denoted IC2xx!
I downloaded the manual for the LLS6000 series regulated PSs.
Generally Lambda did not make their own ICs, just relabeled commercial ones.
It is also possible that they selected the ICs.
However, this IC indeed looks like a custom chip, as the pin-out is non standard!
Assuming that I am looking at the correct schematics, IC101 is a quad op-amp, but with that non-standard pin-out.
It is running from 15V, assuming the note is correct on the schematics.
I would take the old IC out, put in a socket, and wire in a "regular" quad op-amp, like an LM324.
You could also check out the old IC once it is out, test if they behave like op-amps.
If you know the resistor values in the circuit around those op-amps (I did not find any parts list) then you could decide if it needs a FET input op-amp or not.
Good luck, Peter