I went to crypto school in the Army and during my basic electronics course (COBET), an instructor told us about a large radar set that was installed with a “bug” problem. After about an hour it started working properly. The “bug” was the end of a broom handle in the power supply had been lightly sanded off and painted with a resistor color code. Paper clips were inserted into both ends and soldered into the circuitry. The broom handle had become so hot, it became charcoal and transferred the correct OHMS. The student in the test had ignored the burnt paint.
Kilo-volt arcing between the paper clip end pieces charred the dummy resister?