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Monthly Archives: February 2016
Bose® 901 Series II Active Equalizer #68953 Repair
This Bose® 901 Series II Active Equalizer was originally a European unit, designed for a 240V mains supply. Most if not all 240V equalizers with U.S. style plugs were sold on military bases in Germany and elsewhere, and returned with their … Continue reading
Posted in Audio, Bose, Electronics, Projects
Tagged Active Equalizer, Bose, rain city audio, series II
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Bose® 901 Series II Active Equalizer #64364 Overhaul
This Series II Bose® Active Equalizer came through the shop. It had suffered age-related failures in its electrolytic capacitors, and the resistors had drifted with age and moisture to produce the wrong curves. Fortunately, it’s nothing some maintenance can’t solve! … Continue reading
Posted in Audio, Bose, Electronics, Vintage
Tagged Active Equalizer, Bose, capacitor, hifi, repair, series II, transistor, vintage
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555 timer teardown (and a Retrovoltage drum trigger project)
Ken Shirriff’s blog has a fantastic and detailed teardown of a 555 timer, the ubiquitous decades-old timer circuit that turns up in so many places: If you’ve played around with electronic circuits, you probably know the 555 timer integrated circuit, … Continue reading
Posted in Collections, Commentary, DIY, Gadgets
Tagged 555, breakaway derringer, drum trigger, LED, teardown, timer, uncapping
1 Comment
Antique Radio Shop near Kunming, Yunan, China
My friends over at Crimson Lotus Tea sent me this photo of an antique radio shop near Kunming, Yunan in China they ran into during a recent trip. They’re stacked to the ceiling in the shadows. Looks like a fun … Continue reading
Posted in Collections, Photos
Tagged antique radio, antique store, China, shop, vintage radio
2 Comments
Building the SSTRAN Part 15 Low Power AM Transmitter Kit
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
Bose® 901 Series I Active Equalizer #6878 Repair
This early-production Bose® 901 Active Equalizer came through the shop recently for a repair. These Early models were the very first production run, back in 1968, and have a pretty significantly different circuit design from the later models, and feature … Continue reading
Posted in Audio, Bose, Electronics, Hi-Fi, Vintage
Tagged Active Equalizer, audio, Bose, repair, series I
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Retro 1956 Cyclometer VTVM – Hycon Model 615
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 bench meter, cyclometer, hycon, model 615, voltmeter, VTVM
2 Comments
Building a Better Voltage Regulator
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
Posted in Collections, DIY, Electronics
Tagged 7805, current, diy, heat, lm7805, parts, projects, regulator, switching regulator, voltage, waste
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Bose® 901 Series IV Active Equalizer #253288 Overhaul
This Bose® 901 Series IV Active Equalizer came through the shop for a full overhaul. Inevitably over the years, various parts wear out and degrade and can make the equalizer sound bad – or not work at all. Without the … Continue reading
Posted in Audio, Bose, Electronics, Hi-Fi, Projects, Vintage
Tagged Active Equalizer, Bose, repair, series IV
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New Bench Storage
Some pegboards, and wall mounting some parts bins, really cleaned up the benchtop!