The May 2025 gathering of the monthly electronics “Flea at MIT” swapfest featured an excessive number of test instruments. We break them down into oscilloscopes, meters, and signal sources. Click on any image to enlarge in a new tab.
Oscilloscopes
A Tektronix analog modular oscilloscope. The black bezel hides the model number. This unit has a 3A74 four-channel input module and a 3A75 amplifier. Can you tell what model oscilloscope this is? If so, leave a comment.
Hitachi V-252, a 20 MHz analog oscilloscope. There are times when you need real analog persistence.
This is a Krautkrämer USM 2 fault finder. It’s not an oscilloscope, but it has a grid screen. According to the Kroutkrämer Legacy Story, “In the 1950s, the Krautkrämer USM 2 became the world’s first portable, battery-operated ultrasonic flaw detector, revolutionizing field inspection with its unmatched reliability and performance.” Indeed, the USM 2 isn’t even an instrument for electronics. It uses ultrasound to detect mechanical faults such as cracks.
Meters
A Ballantine Labs VTVM, that’s a vacuum tube voltmeter. Yes, people at the swapfest sell vacuum tubes.
General Radio 783-A RF output meter, circa 1960. IET Labs of Boston still services General Radio equipment. You can download the operator manual, which includes a parts list and schematic.
Boonton 8210 modulation meter provides measurements on AM and FM signals. Want to learn more? Download the manual (PDF).
Signal sources
A Rigol DG4102 100 MHz arbitrary function generator. It’s rare to see something at a swapfest that you can still buy new. Rigol lists the price at $1129. The swapfest price was not listed.
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