THE GHOST OF HARPMICS PAST...

Thank you, Charles Dickens, author of "A CHRISTMAS CAROL", not "WHAMMER JAMMER". 'Tis the season...
The subject of this WEEKLY MORSEL put me in touch with a recent piece of my own repair work while serving as a practical lesson to pass along. You may recall that the last MORSEL dealt with volume potentiometers, their cleaning and care, WD-40 do's and don'ts. Turns out I didn't cover everything. What about the incidence of "CRIB DEATH" among the components used in harpmics? Sure, the stories of crystal elements proving dead-on-arrival before their performing lives had even begun are not unusual. I've related examples of ASTATIC MC-151 elements, brand new out-of-the-box and from good families, showing no signs of life at all. What about that other active ingredient in harpmic architecture, the VOLUME POT?
I built a mic for a client. Brushed Nickel JT-30 body and grill, wonderful vintage SHURE Controlled-Magnetic element, a Switchcraft 2501MP thread-on output connector, and a high quality factory fresh 100K potentiometer. Tests great, everybody's happy. For a week. I'm contacted by the owner who's reporting that the mic simply has no output. I requested he return it for testing. Upon dis-assembly I find I'm in agreement with the customer's prognosis. In troubleshooting a situation of this type I suggest going to the heart of the beast first: Establish that the element DOES WORK. Disconnecting the element from the internal wiring and running it to an amp via test leads showed that the vintage C-M was just fine, thanks. So... What could the issue be? With meter and probes I went through looking for an open conductor or a short to ground. The output connector was perfect, solder joints on the volume potentiometer as they should be. With alligator leads I again ran the circuit through the potentiometer. Nothing! Un-threading the pot's mounting nut I pulled the pot, still wired to the element and output connector, and moved it about. On-off-on-off... The mere change in tension of the leads to the pot caused an intermittent signal! OK, replacing the pot's no problem-o, but what was the cause? Turns out that one of the tiny eyelet rivets holding the soldering terminals to the pot was providing deficient continuity -little and no contact. A birth defect...
LESSON? TEST AND RE-TEST EVERYTHING UNTIL YOU ARE CERTAIN YOUR GEAR'S DEPENDABLE!