Bose® 901 Series IV Active Equalizer #223227 Overhaul

From Rain City Audio:

This Series IV Active Equalizer, #223227, just came through for an overhaul. The owner reported it wasn’t making any sounds, just providing a DC offset on the output jacks which was giving his power amplifier some trouble. Time for some new parts!






This equalizer is all original, including the LF353N op-amp chips which were the subject of a service bulletin due to their high failure rates. No wonder it’s having some issues by now!


You can clearly see the residue left on the board from the electrolyte in the capacitor which boiled out and dried on the PCB.





This one got all new electrolytic capacitors and new op-amp chips for proper operation, and now it sounds perfect on all functions and settings. Happy listening!

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