This Bose® 901 Active Equalizer, Series VI, came into the shop recently. These are some of the most recently produced Active Equalizers, although they’re still potentially a few decades old at this point in time. This is only the second Series VI that’s come in for repairs to Rain City Audio. The owner reported it was intermittently crackling after playing for a while.
After all new caps and new op-amp chips, this one sounds great!
RETROVOLTAGE 
What’s the transformer that powers this? I need to replace mine but cant identify what to get.
A drop-in replacement is NLA, but the Tamura 3FD-336 can be configured as an exact functional replacement; primaries in parallel, secondaries in series, junction of the two secondaries becomes the center tap that goes to ground.
THANK YOU! Looks like I can order the part easily online. Does it drop right in? I see the Tamura 3FD-336 is a little different orientation.
No — the holes won’t line up — it’s electrically equivalent though. You’ll need to configure it per the product datasheet with the dual primaries in parallel, and the dual secondaries in series, to give you the 120V input + center-tapped output you need.