Tag Archives: series IV

Bose® 901 Series IV Active Equalizer #269557 Repaired

From the Rain City Audio Repair Blog: Another Bose® 901 Series IV Active Equalizer came in through the shop for an overhaul recently. This one was a bit unusual, and represents a fairly significant deviation from the published service manual. … Continue reading

Posted in Audio, Bose, Electronics, Projects | Tagged , , , | Leave a comment

Bose® 901 Series IV Active Equalizer #221114 Repaired

From the Rain City Audio Repair Blog: Another Bose® 901 Series IV Active Equalizer came through the shop, this one serial #221114. It’s owner reported that it had lost one channel, so it was clearly due for an overhaul. It … Continue reading

Posted in Audio, Bose, Electronics, Projects, Vintage | Tagged , , , , , , , | Leave a comment

Bose® 901 Series IV Active Equalizer #244305 Repaired

Cross-posted from the Rain City Audio Repair Blog: Even the later series Bose® Active Equalizers are getting older, and the Series IV is coming up more and more. I just had another one through the shop, this one sent to … Continue reading

Posted in Audio, Bose, Electronics, Hi-Fi, Projects, Vintage | Tagged , , , | Leave a comment

Bose® 901 Series IV Active Equalizer #246341 Repaired

Cross-Posted from the Rain City Audio Repair Blog: This Bose® 901 Series IV Active Equalizer came through the shop recently with a variety of intermittent issues impacting its performance. These later series equalizers are still getting to be quite old, … Continue reading

Posted in Audio, Bose, Hi-Fi, Projects, Vintage | Tagged , , | Leave a comment

Bose® 901 Series IV Active Equalizer #116907 Overhaul

Cross-posted from the Rain City Audio Repair Blog: Another Bose® 901 Series IV Active Equalizer came through the shop recently. It’s owner shipped it in without the wooden cover for security. This is a bad idea on the Series I/II, … Continue reading

Posted in Audio, Bose, Hi-Fi, Projects, Stereo | Tagged , , , , | Leave a comment

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

Posted in Audio, Bose, Hi-Fi, Projects, Stereo | Tagged , , , , , | Leave a comment

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

Posted in Audio, Bose, Stereo, Vintage | Tagged , , , , , , , | 1 Comment