Tag Archives: Bose Equalizer

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 I Active Equalizer #48344 Repaired

From the Rain City Audio Repair Blog: Another classic Bose® Active Equalizer came through the shop recently for a standard overhaul from sunny California. It’s owner reported that it was performing poorly and channels would cut out. Sounds like a … Continue reading

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Bose® 901 Active Equalizer Series I #17118 Repaired

Cross-Posted from the Rain City Audio Repair Blog: This Bose® 901 Active Equalizer came in through the shop for the standard overhaul service. It was showing its age, as most of these equalizers from Series I and II will do … Continue reading

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Bose® 901 Series I Active Equalizer #33133 Overhaul and Upgrade by Rain City Audio

Cross-posted from the Rain City Audio Repair Blog: Another Bose® 901 Series I Active Equalizer was through the shop lately, serial #33133. It came in working well enough on its original components for an overhaul and upgrade to ensure it … Continue reading

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Bose 901 Series IV #244005 Repair by Rain City Audio

Cross-posted from the Rain City Audio Repair Blog: Bose® 901 Series IV equalizers are coming through the shop more regularly in the past year. It’s expected as these are definitely getting up there in years. This one was sounding muddy … Continue reading

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Esteemed Bose® Model 901 Active Equalizer – Serial #230 Repair

Cross-posted from Rain City Audio: I had the distinct pleasure of working on one of the earliest  Bose® Model 901 Active Equalizers from Series I’s first production run. Serial #230, in fact! It’s made entirely by hand and shows traces … Continue reading

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Bose 901 Series IV Equalizer #202245

A bit different from the run of Series I and Series II that I usually see, I got to fix up this Bose 901 Series IV Active Equalizer which was sent to me from Austin, TX. The Series IV was sold from 1978-1983 and its construction reflects this.

The PCB on this model is single-ended, so can be completely removed from the chassis.

<img class="alignnone" src="https://lh4.googleusercontent.com/-yTJ3z3swIO4/U_wH-zjcj3I/AAAAAAAAkEA/YBDKfs9GTSs/s640/IMG_1459.JPG&quot; alt="" width="640" height="480 Continue reading

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Bose 901 Series II Active Equalizer #67402 Repair

This equalizer got a full overhaul with new 1% precision resistors, electrolytic capacitors, audiophile-grade output capacitors, transistors, gold-plated RCA jacks, 4% silver solder for all connections, a thorough switch cleaning, and computerized frequency response testing and a listening burn-in to verify proper operation. It sounds just fantastic with a very dynamic and life-like presence that really draws you into the experience of the source material, just like the Bose 901 should.

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Bose 901 Series II Active Equalizer #103549

This Bose® 901 Series II Active Equalizer is a part of Rain City Audio’s parts stock and got a full rebuild with upgraded parts and complete and comprehensive testing. All transistors, resistors, film and electrolytic capacitors were replaced, a new neon bulb added, and the controls cleaned and lubricated. This very detailed repair walkthrough has photos showing the drifted carbon composition resistors which can throw off the equalizer’s curve even if all the capacitors have been replaced. Click through for many more photos!

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Bose 901 Series II Active Equalizer #114743 Repair

This Bose 901 Series II Active Equalizer got a full overhaul in the shop with all new capacitors, resistors, transistors and silicon diodes. After a thorough control cleaning, it sounds absolutely fantastic once again and should last for a long time to come.

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