Originally Posted by
kb2vxa
That involves equipment few if any hams have like a HVDC high scale ohmmeter aka an insulation resistance checker or megger. A shorted turn will only turn up in an Ix (excitation current) test, trouble is I have no idea what frequency to use on an RF inductor. That leaves component substitution, the guts to any old current balun will do as long as it fits properly, no crowbars allowed. A crowbar circuit belongs in a power supply, not a tuner. (;->)
You asked a specific question so I gave you a specific answer, however a previously working balun subject to digital low power, typically QRP level should never break down. I suspect an open circuit somewhere, a cold solder joint opened up, a THOROUGH visual inspection is in order. If that fails to turn up anything a continuity test with an analog ohmmeter and wiggly fingers is in order. Put the meter across every joint and switch contact in turn, wiggle the wires, rockers and knobs, and watch the pointer for any twitching you'll never see with a digital meter, they don't react fast enough and tend to bobble. If push comes to shove re-solder every connection. You can find bad joints in any hippie... uh, even top of the line equipment, once upon a time I found a terminal lug in a Collins transmitter with not a drop of solder on it. That wasn't the problem but I soldered it anyway, (;->) a fried screen resistor and shorted tube in one of the IPA stages killed grid current and subsequently power output.
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