Bose® 901 Series IV Active Equalizer #265335 Overhaul

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!

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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!

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