From Rain City Audio:

This rare early-production Bose® 901 Series I Active Equalizer, serial #7790, came through the shop recently for an upgrade. It’s original owner bought this new in 1969 and kept it in use until it began to act up.

This equalizer was serviced several times over its life, one of the most visible was a modification to the rear panel jacks. The owner reported this particular mod was done while he was living in Pakistan.

The repair definitely looks interesting, but electrically, it was done very well. There were some other components replaced as well, including a few transistors..

This one received upgraded output capacitors, and all the transistors, Zener and rectifier diodes were replaced as well.

After all these repairs and a thorough switch cleaning, the equalizer sounds fantastic and will work well for many years to come!