Category Archives: Stereo

EICO Stereophonic Integrated Amplifier HF-81 Repair

Posted on November 7, 2014 by jwk

From the late ’50s, I had this nice example of an EICO HF-81 amplifier come through my shop. These are nice little stereo amplifiers with a built-in phono pre-amp and RIAA equalization and feature about 14W of power output per … Continue reading →

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Boes 901 Series IV Active Equalizer #241792 Refurbishment

Posted on November 3, 2014 by jwk

Bose® 901 Series IV Active Equalizers are getting up there in years now, too, so more and more are coming up for repair. This one came in with a flickering power supply in need of an overhaul. Series IV was … Continue reading →

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

Posted on October 17, 2014 by jwk

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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Phase Linear 2000 Pre-Amp Overhaul

Posted on October 6, 2014 by jwk

Cross-posted from Rain City Audio: I had a Phase Linear 2000 through my shop lately. It was running okay, but had some pops and clicks and the controls weren’t all that smooth. Time for an overhaul before anything worse cropped … Continue reading →

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Sony TA-4650 VFET Stereo Integrated Amplifier Check-Up

Posted on September 24, 2014 by jwk

This repair cross-posted from Rain City Audio: I recently had this Sony TA-4650 in the shop for a check-up. It was reportedly giving static in one channel. That’s trouble on an amp like this – Sony used an ambitious new technology, the VFET, a … Continue reading →

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Marantz 2245 Stereophonic Receiver Rebuild

Posted on September 19, 2014 by jwk

An iconic piece of kit from the golden age of hi fi just came through my shop: the Marantz 2245 Stereophonic Receiver. This fantastic receiver is in pretty good cosmetic shape, but its owner reported that it started acting up – it’d take … Continue reading →

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Bose 901 Series IV Equalizer #202245

Posted on August 29, 2014 by jwk

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

Posted on August 25, 2014 by jwk

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

Posted on July 10, 2014 by jwk

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

Posted on June 26, 2014 by jwk

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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