Category Archives: Projects

KN0CK HF Upconverter Fits Inside the USB Tuner’s Enclosure

Posted on February 19, 2013 by retrovoltage

Marty KN0CK sent me some details to publish about his great looking miniature HF upconverter board for the RTLSDR, the HF Alchemy DVB-T Active HF Upconverter. It’s an incredibly miniature SMT board with an SA612 mixer and SMT oscillator, and … Continue reading →

Posted in DIY, Electronics, Photos, Projects, Radio | Tagged , , , , , , , , , , , , | 11 Comments

Thrift Store Jamo MPA-101 Repair

Posted on February 11, 2013 by retrovoltage

I started working on a Jamo MPA-101 amplifier back in August for a friend and after some early work it sat for a while. He’s re-doing his audio system at home so I spent a few hours to finish troubleshooting … Continue reading →

Posted in DIY, Electronics, Projects, Speakers | Tagged , , , , , , , , , , , , , , , , , , , | 12 Comments

DIY SDR HF Up-Converter by WA7JHZ: Another good choice for your RTLSDR.

Posted on February 2, 2013 by retrovoltage

Reader David Forsman, WA7JHZ, read the round-up of RTLSDR upconverter choices and sent me a photo and build schematic of one he designed which was featured in the January 2013 issue of QST, the ARRL‘s monthly magazine. This circuit up-converts … Continue reading →

Posted in DIY, Electronics, Projects, Radio | Tagged , , , , , , , | 2 Comments

Depression-Era Radio: 1934 Grunow 460 Tombstone

Posted on January 24, 2013 by retrovoltage

I’ve had this Grunow 460 sitting in my queue pending for a little while and it’s finally on it’s way home looking great! There was a fun extra bit of detective work to identify and solve the issues that came … Continue reading →

Posted in Projects, Radios and Tubes, Vintage | Tagged , , , , , , , , , , , , | 2 Comments

First Look: 1934 Grunow 750 World Cruiser

Posted on November 19, 2012 by retrovoltage

I picked up this Grunow 750 “World Cruiser” radio from eBay a little while ago for an incredible deal and now it’s time for it’s turn on the bench. These radios are fairly uncommon and frequently sell for several hundred … Continue reading →

Posted in Electronics, Projects, Radios and Tubes, Vintage | Tagged , , , , , , , , , , , , | 3 Comments

1950 RCA 9X561 Radio Repair

Posted on October 29, 2012 by retrovoltage

A friend I’ve made through the antique radio community is also a repairman himself, but ran into some scheduling difficulty with a piece of work on his bench and sent the chassis over to me for service: an RCA 9X561, … Continue reading →

Posted in Projects, Radios and Tubes, Vintage | Tagged , , , , , , , , | 4 Comments

Shortwave Radio Reception with the RTL-SDR Dongle

Posted on August 6, 2012 by retrovoltage

Need your own upconverter? Click here! I bought and did a quick setup on my RTLSDR dongle using SDR# a few weeks ago, where I used it to listen to FM radio stations around my area and a few public … Continue reading →

Posted in Electronics, Hardware, Projects, Radio | Tagged , , , , , , , , | 3 Comments

New Project: Jamo MPA-101 Amplifier Repair

Posted on August 1, 2012 by retrovoltage

Project’s Conclusion Here My friend brought me this Jamp MPA-101 amplifier he picked up at a garage sale, complaining in only puts out some rumbling and humming. It looks like it’s suffered a failure in the power supply at some … Continue reading →

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First Ever Bose 901 Series 1 Active Equalizer Repair

Posted on July 25, 2012 by retrovoltage

This post is almost 15 years old! Check out this much more recent round-up of Bose 901 Series I and II Active Equalizer repair tips and tricks, and leave a comment if you have any feedback. This post was one … Continue reading →

Posted in Electronics, Projects, Speakers, Vintage | Tagged , , , , , , , , , , , , , , , , | 38 Comments

Identifying Your Bose 901 Series 1 Equalizer

Posted on July 11, 2012 by retrovoltage

Bose 901 Series I Active Equalizers came in two varieties, which can be used interchangeably, but have fairly different circuit designs. It’s simple to tell them apart for ordering parts for a repair with a quick inspection of the inside. Both … Continue reading →

Posted in Electronics, Projects, Vintage | Tagged , , , , , , , , , , , | 4 Comments