An alternative to mechanical vibrator tube or an electronic replacement is the old school method of using the primary circuit of a Model T buzz coil. These coils are readily available and you don’t need one with a good secondary because you just ground that out anyway. Ground the side terminal to the bottom terminal, and insert the coil in the test circuit using the top and bottom terminals. Throw a rheostat and an ammeter in there and you have a coil tester that lets you adjust voltage to see the minimum amperage the test coil will fire at.
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