A Roland custom integrated circuit which is notorious for its high failure rates. The 80017A was used in the Juno 106, the MKS-30 rackmount synthesizer, and the GR-700 guitar synthesizer. The 80017A was a hybrid IC, incorporating the OTA chips used in the famous Roland 1980s VCF circuit, plus the VCA. Physically, the IC is a single-in-line device overcoated with an epoxy encapsulation. The 80017A is long out of production and Roland no longer has any spares.
The reasons why 80017As fail is unclear, but apparently has to do with contamination underneath the epoxy encapsulation. In recent years, some techs have had success in reviving failed units by dissolving the encapsulation using organic solvents such as acetone. However, this does not work every time. The 80017A is marked with a date code, and there are a lot of Internet rumors about which codes are more or less likely to fail, but no one has ever been able to produce any solid data showing a difference.
A company called Borish Electronics offers a clone of the 80017A made with currently available parts. It is a drop-in replacement, physically the same size and not requiring any daughter boards or cabling.