Author Archives: retrovoltage

Philco 42-365 Antique Radio Repair

Posted on December 15, 2014 by retrovoltage

This Philco 42-365 came to the shop in need of major repairs. It was missing its dial string, lamps, and the power transformer had melted down due to a failure in the main electrolytic capacitors. It’s melted and run everywhere, … Continue reading →

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How Speakers Make Sound

Posted on December 3, 2014 by retrovoltage

If you’re looking for a great visual primer on how speakers convert electricity into the music you hear, check out this fantastic animated infographic by Jacob O’Neil at Animagraffs  How Speakers Make Sound

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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

Bose 901 Series IV Active Equalizer #241792 Refurbishment

Posted on November 3, 2014 by retrovoltage

Looking for the latest info on repairing your Bose 901 Series IV Active Equalizer and speaker system? Take a look at the latest in-depth guide with everything you need to know (and more!) Bose® 901 Series IV Active Equalizers are … 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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