Brad Thompson

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The tasteful test bench

In my previous column (“ 5060-9436 ”), I briefly mentioned the inevitable demise of user-repairable test instruments due to age and the dwindling numbers of parts-donor instruments. Unfortunately, current-generation instruments include custom ICs (ASICs), and many manufacturers no longer offer service manuals or schematics. All this points to a future in which hardware hackers... More

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5060-9436

That’s the Hewlett-Packard part number for the front-panel push-button key switches used in the nonworking HP-8656B 0.1–990-MHz signal generator I recently added to my collection of obsolescent test equipment. As received, all of the HP-8656’s front-panel displays and indicator LEDs lit up like a Christmas tree. Replacing a missing low-voltage filter capacitor restored a... More

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String 'em up!

With apologies to Fred Foy, Brace Beemer, and the writers of  “The Lone Ranger” radio program, “Return with me now to those thrilling days of yesteryear. The Analog Dial Pointer rides again!”…or not, if you’re unable to repair the damned thing. If you’ve never peered inside the cabinet of a 1950s-vintage radio, you may have missed... More

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One-inch wonders

Introduced by RCA (Radio Corporation of America) in November 1936, the 913 CRT (cathode-ray tube) created a minor stir in the electronics community. RCA initially priced the 913 at $5.60 (approximately $87 today when adjusted for inflation), which was a bargain, considering that RCA’s 3-in. 911 CRT cost four times more.To a casual observer, the metal-jacketed 913 resembled RCA’s... More

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Old dog, newer trick

Although mostly obsolete, the vacuum tube still has its adherents among audiophiles, test-instrument collectors, amateur-radio fans, and those curious about the physics of active devices. Given that a family of characteristic curves is worth a thousand data points, being able to view a device’s behavior enhances a small laboratory’s capability. Vacuum-tube curve tracers are... More