[Milsurplus] A bit more leaky caps and trimmers

[CL in NC]

I agree that the Micamolds should all be looked at, with not just an ohm meter, put volts on them from a cap checker or a bench supply  What shows up as 3 meg on an ohm meter, might look like a short when it has a couple hundred volts on it.  Any leakage will affect a circuit operation, saying the leakage is acceptable on perhaps, screen bypass, stage after stage, and the cumulative effect is a receiver that is just not quite up to snuff. Any leakage in a coupling cap is asking for trouble, I had a Heath RX1 with a 470pf mica IF coupling cap that read open on a Triplett meter on RX10,000, but showing just a hint of an eye closure leakage on an Eico cap checker, at its rated voltage, compared to a new one.  Replacing it made the receiver sense improve markedly from what it was, and it was pretty good before.

I have a method to repair the Johnson Type J and M trimmers, and their clones from other manufacturers that use the collar on shaft retainer, when the collar has broken free.   You have to remove it from the rig of course, and it is best to remove the collar, clean the shaft and inside the collar to allow  friction free movement.  Observe the construction of the cap and you will see you can put the cap in a vise, with the back of the rotor shaft on one jaw and using a proper support on the ceramic side at the points the stator is soldered in, not on the ceramic, with a spacer that keeps the rotor shaft from contacting the jaw on he ceramic side, slowly close the vise until the rotor and stator are centered again, and the spring is compressed.  Position the collar against the bearing surface reheat and solder, or do what I do.  The idea is to stake the collar to the shaft using a bit of copper wire.  While the collar is off the shaft, drill through it with a drill diameter the same size or very close to the copper wire you will be using.  Put it back on and compress the cap in the vise, when in the right spot, position the collar, mark the shaft, remove the cap and collar, cross drill the shaft at your mark.  Put it back in the vise and compress it to center the holes.  If your drilling was off a bit, carefully run it through collar and shaft and then insert the wire.  When you release the vise, you can remove it and now solder it.   I was tweaking up my Motorola 6 meter D41 series, and just  about every trimmer broke at the collar when an adjustment attempt was made.  I submitted this repair  as a 'Hint and Kink' to QST, complete with pictures, I got a 'Not of interest to our current membership' rejection letter, I have a lot of those.  They would probably have to write and article about what a trimmer cap is first.

And on a closing wiseacre note, I looked in my milsurp gear and could find no nanofarads, just micro and pico.  What happened? To many zeroes after the decimal get confusing to the modern engineer?  Remember, the slide rule designed Saturn V never blew up with people on top of it, the computer designed Challenger, not so fortunate.

Charlie, W4MEC in NC