Fix it for fun

Brad Thompson, Contributing Technical Editor -- Test & Measurement World, 1/1/2001

When was the last time you repaired anything electronic for the sheer fun of it? Chances are if you work as a field-service engineer or an MRO (maintenance and repair organization) technician, you'll answer, "Fix electronics for fun? Are you crazy?!"

Well, thanks to the Internet, it's easy for us crazies to form communities. My favorite newsgroup, rec.antiques.radio+phono, provides an online hangout where an eclectic group of amateurs and professionals discuss, diagnose, and dissect ancient electronics.

Although most of the newsgroup's messages concern radios and phonographs built around vacuum tubes, there's a surprisingly strong undercurrent of interest in vintage test instruments and how to use them. You can often repair a tube-era radio by replacing a tube or a few capacitors, but you'll need at minimum a multimeter and signal generator for more-extensive diagnoses.

Today, good DMMs are available for $50 or less, but where are the other cheap instruments? The demise of electronic-kit manufacturers (e.g., Heath, EICO, and Precision Apparatus) left a vacuum at the low-cost end of the instrumentation market. Newsgroup readers in search of inexpensive test instruments for radio repairs frequently purchase used equipment, only to find that they must repair the instruments-and learn how to use them-before proceeding.

Alan Douglas, an electronics historian and frequent newsgroup contributor, has written a book (Tube Testers and Classic Electronic Test Gear) describing pre-1970s instruments. While Douglas focuses primarily on the arcane arts of tube-tester operation and vacuum-tube testing, his book offers enough of an overview of other instruments (e.g., signal generators, capacitor testers, and grid-dip meters) to get first-timers started. But in years to come, we'll run out of antique test equipment sooner than we'll run out of test targets-our beloved All-American Fives and cathedral radios.

So, here's your assignment: Design (for the fun of it, of course) a $50, AM- and FM-modulated, general-purpose signal generator kit covering 100 kHz to 150 MHz. It should be simple enough for a beginner to assemble and be resistant to tube-level accidental overvoltages.

It's a crazy project, huh? Hey, it's almost as crazy as fixing radios for fun. T&MW