Category Archives: Electronics

Building a Better Voltage Regulator

Posted on February 17, 2016 by jwk

Glancing through my feeds, I stumbled across a note on The Paleotechnologist describing a new replacement for the venerable LM7805 linear regulator IC. It turns up in a ton of devices, pretty much anything with a medium-current 5V rail including … Continue reading →

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How to Read Capacitor Codes

Posted on January 24, 2016 by jwk

I ended up with a massive stash of mil-spec CDE Mica caps recently, and was searching for a refresher on decoding their military part numbers like “CM05FD221GP3”, since the caps came marked for their values but not their voltage ratings. … Continue reading →

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

Posted on January 20, 2016 by jwk

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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Philips High Fidelity Laboratories 673 Tuner Repair and Alignment

Posted on January 4, 2016 by jwk

From the Rain City Audio Repair Blog: This Philips 673 tuner just came through the shop for an overhaul and adjustment. It was working for the most part but the alignment had shifted and there was room for improvement on … Continue reading →

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Bose® 901 Series IV Active Equalizer #219533 Overhaul

Posted on January 2, 2016 by jwk

From the Rain City Audio Repair Blog: This Bose® 901 Series IV Active Equalizer, serial #219533, came through the shop for an overhaul. The owner was reporting the left channel went out, so it’s clearly time for an overhaul! A … Continue reading →

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HH Scott 233 Stereo Integrated Amplifier Overhaul

Posted on December 31, 2015 by jwk

From the Rain City Audio repair blog: I was lucky enough to get to work on a very nice Scott 233 stereo integrated amplifier. This example was wonderfully well preserved, coming out of a storage unit looking like it had … Continue reading →

Posted in Audio, Electronics, Radios and Tubes, Stereo, Vintage | Tagged , , , , , , | 7 Comments

Assembling Transistor Radios in 1955

Posted on December 18, 2015 by jwk

Here’s a great documentary short from 1955 showing how portable transistor radios were assembled. It’s super retro! (2:35) Want to learn more about transistors? Just a few years later the US Information Agency produced an 8-minute short film about the … Continue reading →

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Bose® 901 Series IV Active Equalizer #269557 Repaired

Posted on December 10, 2015 by jwk

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 →

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Bose® 901 Series IV Active Equalizer #221114 Repaired

Posted on December 3, 2015 by jwk

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 →

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What do we have here?

Posted on December 1, 2015 by jwk

I was reading about how to build a capacitor checker from the December 1959 issue of Popular Electronics and stumbled across something that looked very familiar. I know that shape. Nearly identical to a Bose® 901 Series I/II cabinet, and even … Continue reading →

Posted in Audio, Bose, Collections, Commentary, DIY, Electronics, Vintage | Tagged , , , , , , , , , , , , , | 2 Comments