Keeping your world up and running.®

It all began with a 22.5-volt Crosley radio

A tale of technical curiosity

March 2013

1924 Crosley model 50 radio

Rare find: a 1924 Crosley model 50 radio. Photo courtesy of Steve's Antique Technology

One of the things we've discovered over the years is that a lot of Fluke customers developed technical curiosity long before they got paid for it. Such is the case with Steve Johnson, from upstate New York.

Johnson's professional resume reads like a technology road map of the last four decades, including stints as a sound engineer for rock-and-roll shows, servicing commercial radio systems, building custom test equipment for the US Department of Defense, as a Web designer, and as an IT director for the last dozen years before he retired in 2010.

But before all of that, Johnson became fascinated with electronics - at about the age of eight. His interest evolved into an impressive collection of vintage radios and, later, test equipment from companies like Supreme Instruments, Simpson Electric Company, Triplett Meter Company, and many more.

The gift that started it all

Johnson's first foray into the world of vintage radios began at 16 when a friend of his father's gave him a Crosley radio, circa 1924. "It was a one-tube job that only took headphones because it wasn't powerful enough to power a speaker," says Johnson. "It had a book capacitor, which was two cast-iron plates that opened and closed on a piece of mica, to change the stations. I was amazed that something that simple could actually pick up radio. That got me hooked."

Johnson studied electronics in high school and college and embarked on a long and varied career, ranging from electronics service and design to computer networking. During that time he expanded his collection of antique radios and vintage record players. But he didn't collect these items just to look at them; his goal was to restore them to working order if at all possible.

All roads lead through the capacitors

1924 Crosley model 50 radio

Johnson restores radios and test equipment using a wide range of testing equipment. Photo courtesy of Steve’s Antique Technology

The first challenge with the radios was the capacitors. Radios are inherently full of capacitors, and after many years a lot of them - especially the older paper capacitors - go bad. You can't just plug in a 70-year-old radio and see if it works, because the capacitors will likely fail and could destroy other components.

"When you get a piece of equipment from the 1930s or '40s you have to bring up the AC power slowly on a Variac," says Johnson. A Variac, or variable auto transformer, allows varying the voltage input to control how much power is applied to the radio.

"As you bring up the AC power, you monitor the current draw with a meter to see if it's coming up steadily or if it starts increasing quickly," says Johnson. "If it starts to increase quickly, that's usually a sign that a component is failing."

He uses Fluke 8000 series digital multimeters to measure voltage on the devices he's testing and to set power supply voltages. If the meter indicates that a component is failing, he first checks the vacuum tubes.

"If a tube shorts it can take out other components, so it's a good idea to run a shorts test on the vacuum tubes first." For that he uses a military I-177B tube tester from the early 1950s. Vacuum tubes are still readily available, so if tube shorts are the problem the fix is easy.

If the problem isn't a tube, he next tests the capacitors and resistors. "Capacitor shorts can take out a transformer, and if a power transformer is gone in a radio, it's pretty much toast," says Johnson.

Expanding the collection

1924 Crosley model 50 radio

This Supreme Instruments Counter Tube Tester (circa 1934) started Steve Johnson’s test tool collection. Photo courtesy of Steve’s Antique Technology

After collecting radios for a few decades, Johnson came across a photo online that would profoundly change the direction of his collection. "I found a picture of a Supreme Instruments tube tester from the early 1930s," recalls Johnson. "It was such a unique item, I had to have it." That was the beginning of his vintage test equipment collection. As he collected more test equipment he sold off many of his antique radios to make room for the new items. He also started collecting vintage factory service manuals and schematics.

Today his collection of test equipment spans the period from the 1920s to the 1950s, and the Supreme tube tester is still the cornerstone. "It's a very rare piece. There are only a few of them and the others are mostly in museums," Johnson says.

Johnson's collection includes other tube testers, as well as transducers, signal generators, volt/ohmmeters, and radio bench test gear from several manufacturers. He's found that restoring vintage test equipment can be easier in some ways than restoring radios because the test equipment tends to have fewer capacitors. However, back in the '20s and '30s many manufacturers updated test equipment models without documenting the changes or changing the model numbers.

"Sometimes they made the same model for six or eight years, but there would be ten different versions of it. So what you'd find in the test equipment and what was shown in the schematic could be two entirely different things," Johnson says.

These days, not all of his purchases are vintage. To calibrate his bench equipment, he recently purchased a new Fluke 87V digital multimeter (DMM). "The 87V is the king on the bench. Everything else is compared to it," says Johnson. If he's restoring an old vacuum tube volt meter, he compares the readings from his Fluke 8000 series to those of the 87V to make sure they are comparable. "Most of the stuff I do doesn't require high accuracy but I like the equipment to be on target. So even though I'm using a vacuum tube voltmeter from 1956, I want to know that what the meter is showing is accurate, so I use the Fluke 87V to bench mark that."

You can view pictures of many of Johnson's collectibles at www.stevenjohnson.com, and see vintage service manuals at www.antiqueradioschematics.org or www.TheSchematicMan.com. If you're interested in starting a collection of your own you might also want to take a look at Johnson's "What's it worth?" column for Electronicproducts.com.