This article examines the “curtain burner” or those 1930s radios that were furnished with a resistance line cord that supplied vacuum tube filament voltage as well as power the radio itself. I’ll look at how possibly restoring these types of radios can be problematic, and how to safely restore them.
Are you an audiophile with a yearning to build kits reminiscent of the old HeathKits? If so, then this high-end tube amp kit may be what you’ve been waiting for. I think you’ll appreciate the value proposition of this eight watts per channel single-ended stereo amp based on a pair of 300B or 2A3 triodes.
Among the best-kept secrets in Great Britain during World War II was a 600 kW medium-wave transmitter which was codenamed “Aspidistra.” The transmitter would disrupt the German war machine through misdirection and fake news.
Sidereal time is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it’s possible to easily point a telescope to the proper coordinates in the night sky. A fellow reader of N&V contacted me about a digital clock that counted and reported standard and sidereal time, both in 24 hour format. It needed some work, and he sent it to me. Here’s how the restoration went.
In Part 1 of this series, I covered basic sweep alignment theory and construction/operation of an all-in-one sweep alignment instrument I dubbed the WhippleWay Sweep Alignment Board (or WSAB for short). In Part 2, I’ll describe sweep alignment procedures for AM and FM radios and give an actual example of each.
The popularity of repairing and restoring tube radios has highlighted the need for a variety of test instruments. After repair or restoration of a radio, the final step is often alignment. For an AM radio, a signal generator and voltmeter will do a good job. But with an FM radio, using a signal generator and voltmeter does not always produce the best results. So, I came up with my own design using a digital signal generator module, Arduino processor, and digital display.
Even though they were invented over 100 years ago, vacuum tubes are still interesting, rewarding, and worthy of investigation. Plus, building with tubes reviews the history of the technology and promotes an understanding and appreciation of its development.