Category Archives: Vintage

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 →

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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 →

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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 →

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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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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 →

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HP 143A Wide Screen Oscilloscope Mainframe Restoration – Part 2

Posted on October 15, 2014 by retrovoltage

Part 1 I’m continuing to work on getting my HP 143A ocsilloscope mainframe fixed up as a dual-trace X-Y display. A lot of the time has been spent on reading and researching, but I’ve picked up an important tool that will … Continue reading →

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Harmony H500 Solid State Guitar Amplifier Repair

Posted on October 10, 2014 by retrovoltage

And now for something a little different, this time it’s a vintage guitar amplifier: the Harmony H500. The owner sent it to the shop out of the cabinet to be serviced since it quit putting out any sound. It’s a … Continue reading →

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DIY Replacements for Vintage Couplets and Printed Electric Circuits

Posted on October 9, 2014 by retrovoltage

Starting in the ’50s, they’d figured out how to start miniaturizing components. “Couplets” and “printed electric circuits” started showing up in equipment around then. These components were combinations of several resistors and capacitors in a single package. Like most components … Continue reading →

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