From Rain City Audio:
This Bose® 901 Series IV Active Equalizer, #265335, just came through the shop for an overhaul. It’s owner bought this equalizer as a part of getting his Bose® system back up and running and sent it right to Rain City Audio reporting the left channel was out. Let’s get that fixed up!
Inside, this one had been serviced at some point, and the service bulletin recommendation was followed. There are a handful of different electrolytic capacitors installed, and the op-amp chips are RC4559Ns with a date code of 44th Week 1981, several years after this unit was originally manufactured. The RC4559 is one of many op-amp chips with the same standard pin-out and overall similar functionality. In this case, the owners requested an upgrade to new model TI precision op-amps for even better performance and lower distortion.
In addition to new chips and new electrolytic capacitors, this unit got a new set of rubber feet on the bottom to replace the existing set which was had one missing member. After all this, it works and sounds great!