Tech Square

Posted by strijw426 (A) on October 08, 2011 at 16:45:24

In Reply to: RE: Heathkit IB-2 Impedance Bridge posted by strijw426 on October 04, 2011 at 16:11:42

I discovered that the CRL Switch Dial (the one at the upper right side) which has numbers from 0-9 had a crack in the plastic where the set screw was located. It would slip on the shaft and the set screw could not tighten enough to stop this. I finally used a small round file to rough up the shaft surface and the inside of the knob, made sure the switch was in the "0" position fully counter-clockwise and pushed the knob onto the shaft (with the "0" aligned with the pointer) with a small drop of super glue (cyanoacrylate). After just a few sedonds it was firmly attached and I screwed the set screw down against the shaft for good measure. After this the unit was fully functional and worked as designed.

Someone years ago had attempted a repair to the knob by winding a piece of hook-up wire around it, tightened it and soldered the wire, then had added model airplane type cement to it. That was not successful in the long term.

If it ever breaks loose again I have a plan "B" in mind - order a suitable 1/4" shaft knob from Mouser Electronics, drill out the top and fasten the OEM knob to the new knob with small screws, then use the set screw of the new knob to fasten to the shaft. Mouser has aluminum as well as plastic knobs. They even have some plastic knobs that are the same shape and size as the OEM knobs used for the Generator Level, Generator Switch, Detector Switch, AC Zero Control, Function Switch and Range Switch.