A complete functional test required rotating each pot while monitoring its wiper terminal voltage. This test  was quickly and easily done at room temperature, but having to test 28 pots at -75" C and +70° C in a  minimum amount of time required a different approach. A gang fixture was designed and constructed with  a stationary plate that supported up to 36 MIL-PRF-39023-style pots (Figure 6). A driveshaft turned a  central crank arm which rotated a second plate eccentrically. The eccentric rotation of the second plate  was converted into rotation of the individual pots by a crank arm on each pot shaft.  Figure 6. Two views of gang fixture with 28 pots installed, before being placed in chamber  This gang fixture was set up in a dry nitrogen purged thermal test chamber employing electrical heating  and liquid nitrogen cooling. The driveshaft passed through an opening in the chamber wall to a gearmotor.  With this set-up, electrical performance was rapidly verified at the temperature extremes in both the CW  and CCW directions. The following lesson was learned:  LESSON 8. Don't put all your eggs in one basket. Trying out a new test procedure on all the  irreplaceable flight pots in one batch is risky. It is a great deal of work to recertify potentially  compromised pots for flight. Instead prove out the test procedure with a few disposable EM pots.  Complete the testing and data analysis, then revise the procedure with lessons learned before  applying it to any flight pots.  The Ripple Effect, Part II  The next step was to check for any "scratchy, detent" feel as each pot shaft was rotated. This was a very  delicate task as the torque required to rotate each ball-bearing supported shaft was at most a couple of  millinewton-meters. With no sensitive torquemeters available, I turned off the laminar flow benches in the  clean room to eliminate their noise and vibration, turned off most of the lights to get rid of the powerline  buzz, and ripped the thumb and index finger off my right glove. One by one I took each pot in my hands  and rotated the shaft back and forth with my bare fingers, eyes closed and concentrating. Soon I was  writing another PFR to document the very weak detent that was felt as the shaft of:  a) SIN 1027 was rotated by hand through the -190 degree CW shaft orientation, and  b) SIN'S 1021 and 1036 were rotated by hand through the -240 degree CW shaft orientation  In each case the shaft orientation where the detent was felt did not change, even after many shaft  rotations; clearly it was not caused by a bad ball in the bearing or a bad inner race. The detent on SIN  1027 occurred at the -190 degree CW shaft orientation which placed the wiper in the electrical dead zone  of the pot so damage from high current should not have been a problem. The detents on SIN 1021 and  1036 occur at the -240 degree CW shaft orientation which placed the wiper far enough away from the  "CCW" end of the resistance element that damage from high current should not have been possible.  Functional testing at room temperature, -75" C and +70° C had already verified the required electrical  performance for these three pots. X-ray images revealed no macroscopic wiper damage, though it was  not possible to tell from the X-ray images if the conductive plastic disk was damaged. How could I be