Tag Archives: Active Equalizer

Bose® 901 Series I Active Equalizer #28322 Repaired

From Rain City Audio: This Bose® 901 Series I Active Equalizer #28322 came through the shop for an overhaul. The original series, these Series I Active Equalizers have the oldest electronic components which are nearly universally out of their service … Continue reading

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Bose® 901 Series II Active Equalizer #81471 Repair

From Rain City Audio: This Bose® 901 Active Equalizer, Series II #81471, just came through the shop for a repair. It’s owner sent this one all the way from Ontario, Canada for expert repair from Rain City Audio. This one … Continue reading

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Bose® 901 Series II Active Equalizer #68953 Repair

This Bose® 901 Series II Active Equalizer was originally a European unit, designed for a 240V mains supply. Most if not all 240V equalizers with U.S. style plugs were sold on military bases in Germany and elsewhere, and returned with their … Continue reading

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Bose® 901 Series II Active Equalizer #64364 Overhaul

This Series II Bose® Active Equalizer came through the shop. It had suffered age-related failures in its electrolytic capacitors, and the resistors had drifted with age and moisture to produce the wrong curves. Fortunately, it’s nothing some maintenance can’t solve! … Continue reading

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Bose® 901 Series I Active Equalizer #6878 Repair

This early-production Bose® 901 Active Equalizer came through the shop recently for a repair. These Early models were the very first production run, back in 1968, and have a pretty significantly different circuit design from the later models, and feature … Continue reading

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Bose® 901 Series IV Active Equalizer #253288 Overhaul

This Bose® 901 Series IV Active Equalizer came through the shop for a full overhaul. Inevitably over the years, various parts wear out and degrade and can make the equalizer sound bad – or not work at all. Without the … Continue reading

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Bose® 901 Series IV Active Equalizer #501554 Overhaul and Upgrade

From the Rain City Audio Repair Blog: This Bose® 901 Series IV Active Equalizer, serial #501554, came into the shop with the owner reporting that it loses output on one channel and the sound degrades the longer it is powered … Continue reading

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