Author Archives: retrovoltage

Boxed Kit Amps’ Gobo Stereo Amplifier Build and Review

Posted on November 26, 2014 by retrovoltage

If you’re a subscriber to Nuts and Volts Magazine, check out my article in the December 2014 issue where I build, test and review the Boxed Kit Amps Gobo Stereo Amplifier, a great little desktop reference amp for any skill … Continue reading →

Posted in Audio, Commentary, DIY, Electronics, Gadgets, Hi-Fi, Projects, Stereo | Tagged , , , | 2 Comments

VD-1221 Replacement Substitute Diodes

Posted on November 25, 2014 by retrovoltage

VD-1221, VD-1212, VD-1220, VD-1222, and many other vintage multi-junction diodes probe to failure, which are used in bias and RF mixer circuits, can be easily replaced by series combinations of 1N4148 diodes for reliability and longevity. Continue reading →

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Vintage Schematic Mistakes

Posted on November 21, 2014 by retrovoltage

Every once in a while, you run into places where a drafting tech made some mistakes on the schematics. This one was a Philco 42-360 radio, which has the wrong tube called out in the tube line-up vs. the schematic. The … Continue reading →

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Harman/Kardon Control Amplifier A-401 Restoration

Posted on November 19, 2014 by retrovoltage

This little Harman/Kardon Control Amplifier, model A-401, just came through the shop for a full overhaul. It was in a pretty sorry state to begin with – one channel distorted, one barely gasping for air, and a world of scratchy … Continue reading →

Posted in Audio, Electronics, Hi-Fi, Projects, Stereo, Vintage | Tagged , , , , , , , , , , , , , | 8 Comments

EICO Stereophonic Integrated Amplifier HF-81 Repair

Posted on November 7, 2014 by retrovoltage

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 →

Posted in Audio, Hi-Fi, Projects, Stereo, Vintage | Tagged , , , , , , , , , , , , | 1 Comment

Boes 901 Series IV Active Equalizer #241792 Refurbishment

Posted on November 3, 2014 by retrovoltage

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 →

Posted in Audio, Bose, Hi-Fi, Projects, Stereo, Vintage | Tagged , , , , | 1 Comment

Vintage Engineering is Beautiful

Posted on October 30, 2014 by retrovoltage

EL84 output tubes in an EICO HF-81 integrated stereo amplifier.

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Marantz 2270 Stereophonic Receiver Overhaul

Posted on October 26, 2014 by retrovoltage

I just had a great stereo receiver through the shop for repairs, the Marantz 2270. It’s the big brother to the Marantz 2245 I had through the shop a little while ago – mostly the same front-end circuitry, but with … Continue reading →

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Use Copper Shielding Tape to Protect Dial Strings from Hot Tools [Tips and Tricks]

Posted on October 24, 2014 by retrovoltage

Dial strings are, quite frankly, about the worst things in the world. They’re usually a complex and finicky mechanical system parked right in the middle of an otherwise straightforward electrical project, and if a string breaks good luck getting it … Continue reading →

Posted in Commentary, DIY, Tips and Tricks, Tools | Tagged , , , , , , , , , | 1 Comment

Toshiba 11H-540F Tabletop Transistor Radio Overhaul

Posted on October 20, 2014 by retrovoltage

I recently got to work on a little tabletop transistor radio from the late ’60s, maybe 1970 at the latest, from Toshiba: the 11H-540F. Not the catchiest name, but it was near the top of its model line-up featuring 11 … Continue reading →

Posted in Audio, Electronics, Vintage | Tagged , , , , | 5 Comments