Category Archives: Electronics

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 →

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

Reviewing the Gemtune APPJ PA1501A 6AD10 Stereo Tube Amplifier

Posted on August 17, 2016 by retrovoltage

I recently picked up an interesting little tube amp via a group buy on Massdrop, the Gemtune APPJ PA1501A stereo tube amplifier. Try saying that three times fast! It’s a cute little single-ended stereo tube amp using a pair of 6AD10 … Continue reading →

Posted in Audio, Commentary, Electronics, Hi-Fi, Stereo, Toys | Tagged , , , , , , | 15 Comments

Bad Caps in Everything

Posted on July 20, 2016 by retrovoltage

I just had a bit of a scare with my Audio Precision analyzer. The 2004-era Dell OptiPlex GX270 which drives the AP hardware decided it would refuse to power up – just flashing the “ON” light for a fraction of … Continue reading →

Posted in Computers, DIY, Electronics, Test Equipment | Tagged , , , , | 3 Comments

DBX SFX-10

Posted on May 31, 2016 by retrovoltage

I saw this interesting set of speakers on Craigslist, but they sold quickly before I could investigate. They’re the DBX SFX-10s. There’s a very interesting article about their design in the May 1990 issue of The BAS Speaker, the publication … Continue reading →

Posted in Audio, Electronics | 6 Comments

Bose® Active Equalizer Test Platform

Posted on April 13, 2016 by retrovoltage

This project is going to take a while since I’m slammed in the shop, but I’m in the process of converting a Bose® 901 Series I Active Equalizer to  a test platform. With sockets for the transistors, and clip connections … Continue reading →

Posted in Audio, Bose, DIY, Electronics, Stereo, Test Equipment | Tagged , , , , , | 3 Comments

“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

Building the SSTRAN Part 15 Low Power AM Transmitter Kit

Posted on February 21, 2016 by retrovoltage

Have a bunch of old tube radios, but nothing good on the air in your area? That’s a common problem, and SSTRAN has the solution! I just built one of these to give as a gift, and thought I’d write up … Continue reading →

Posted in DIY, Electronics, Projects, Radio | 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

Building a Better Voltage Regulator

Posted on February 17, 2016 by retrovoltage

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 retrovoltage

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 →

Posted in Commentary, DIY, Electronics | Tagged , | 1 Comment