Category Archives: Vintage

Everything to Know about the Bose 901 Series III Speakers & Active Equalizer Repair

Posted on July 31, 2026 by retrovoltage

A look at the Bose 901 Series III speaker system and Active Equalizer, with a brief history and explanation, plus repair tips and tricks, schematics, and parts list with direct links to buy. Continue reading →

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

1961 Audax CA-70 “Sonoteer” Speaker Refurbish

Posted on July 22, 2026 by retrovoltage

This set of 1961 Rek-o-Kut Audax CA-70 Sonoteer speakers got a full overhaul inside and out. Come learn about these interesting mid-century open baffle hi-fi speakers from a little known manufacturer and see how they turned out with detailed interior and exterior photos, and the original advertisement from September 1961. Continue reading →

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

HH Scott HHS-20 “Scotsman” Receiver Overhaul

Posted on January 27, 2017 by retrovoltage

A local repeat customer recently brought in his old HH Scott HHS-20 receiver for an overhaul. It worked a few years ago when he put it away, although not without a few issues of its own, and when he dug … Continue reading →

Posted in Audio, Electronics, Projects, Stereo, Vintage | 3 Comments

A Surprise in a Re-Stuffed Capacitor

Posted on October 18, 2016 by retrovoltage

I was recently re-stuffing some capacitors for a radio. It’s not something I do often, but I’ve accumulated a pile of pulled vintage caps over the years so I have some on hand if a customer requests the most detailed … Continue reading →

Posted in DIY, Electronics, Radios and Tubes, Vintage | Tagged , , | 3 Comments

Music Minder Automatic Power Controller for Hi-Fi Systems

Posted on August 24, 2016 by retrovoltage

Mixed in with some other gear I’m servicing, I found this old Music Minder power box. It’s not all that obvious what it’s for at first glance! Some digging around found an explanation in the June 1958 issue of Popular … Continue reading →

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Would you look at that!

Posted on August 9, 2016 by retrovoltage

It’s pretty, but this 12BA6 tube has amplified for the last time. Vacuum failure has led to a gas intruding into the vacuum, and it makes a great light show when it’s being tested! As cool as it looks, this would cause … Continue reading →

Posted in Photos, Radios and Tubes, Vintage | Tagged , , , | 1 Comment

“Won’t that ruin the vintage sound?”

Posted on March 16, 2016 by retrovoltage

Audio as a hobby sits in an interesting place in the world. There are hard numbers and objective measurements made with lab equipment on one end, and on the other end you have the subjective and variable linguistic descriptions assigned … Continue reading →

Posted in Audio, Commentary, Electronics, Hi-Fi, Vintage | Tagged , , , , , , , | 3 Comments

Retro 1956 Cyclometer VTVM – Hycon Model 615

Posted on February 19, 2016 by retrovoltage

A pretty cool, very rare piece of test equipment turned up on eBay recently: a 1956 Hycon model 615 AC/DC VTVM. This was a precursor of today’s digital, using analog servo circuitry to drive the numeric digit display. These were … Continue reading →

Posted in Electronics, Gadgets, Test Equipment, Vintage | Tagged , , , , , | 2 Comments

Philips High Fidelity Laboratories 673 Tuner Repair and Alignment

Posted on January 4, 2016 by retrovoltage

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 the sound quality. Philips designed this tuner … Continue reading →

Posted in Audio, Electronics, Radio, Vintage | Tagged , , , | 3 Comments

HH Scott 233 Stereo Integrated Amplifier Overhaul

Posted on December 31, 2015 by retrovoltage

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 just left the showroom floor. Unfortunately, though, … Continue reading →

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