The AM Forum

Early this morning, before I had to attend to "responsibilities", i.e. the YL, I was able to slip away to the Union, Maine hamfester.
 
Nice gathering and I returned home - what a surprise - with more radio stuff.
 
One of the finds was a very nice Johnson Kilowatt Matchbox antenna tuner.
Considering it is over 50 years old, it was in very fine business condition, with one problem.
 
Now, if you work on older gear chances are you are going to encounter the same problem which I found with my new Matchbox.
Seized shafts.
Yes, its not just a male problem, it happens to radio gear as well.
The bandswitch on the Matchbox was seized solid from time and disuse.
I tried turning it, but it was stiff and I was concerned that I would crack the knob.
 
So, after removing the nearly 50 some screws which hold the box together - really, count them - I was able to inspect the problem.
There, buried deep inside the tuner was a nice heavy duty ceramic two section switch connected to taps on the inductor.
The switch functions as a bandswitch, changing the inductor tap with each band selected.
 
My first thought was oil, so I liberally baptized the switch with penetrating oil - no success.
Next I got out the universal problem solver i.e. the hammer and tried gently tapping on the shaft, still no luck.
So I removed the inductor and the switch from the cabinet, even more screws, and after 45 minutes of effort I had the switch on the workbench in front of me.
I tried oiling again, still no luck.
I considered disassembling the switch for a good cleaning, but could not rotate it to access the retaining screws.
Then it struck me, I could try to heat it.
I reached for the trusty heat gun and fired it up to moderate heat.
I carefully heated the front section of the switch and then the rear section, not super hot, but warm enough not to touch.
Like magic the once seized switch rotated with little effort, clicking in firmly at each detent.
I applied some more oil, wiped off the excess, and then reheated the switch.
It seems the heat allowed the oil to be drawn into the switch, worked like a charm.
 
So, if you are ever faced with a stuck volume control potentiometer, switch, or shaft, and oil does not work, try a little from a heat gun or hair dryer.
 
Hope this helps someone else out.
 
 
73 Bruce W1UJR

This needs to go in the "Restoration" or "Hints and Kinks" section.

Thanks for that, Bruce.  Sometimes switches won't turn because the contacts have been welded... *that's* no fun, believe me.  :evil:

Heat from a soldering iron can be used on metal shafts. I have also found that tuner cleaner will work on frozen shafts. I think it softens up the old dried out grease

We have some stuff that you can pick up at the hardware store. Its called Kroil. Advertised as the 'Oil that Creeps'. We commonly refer to it as Weasel Piss since it migrates into everything. It is a solvent so it is good around moisture. It has a distinct smell to it so sometime we will call it Millwrights' Aftershave. It works well in a chemical factory so I would imagine it would work easily on frozen shafts.

One of the best penetrating oils I have used is the PB Blaster brand and along with a little heat it works wonders.

Roy - You aren't kidding! I used to think all penetrating oils were the same. Not so with PB Blaster. The stuff is really superior to anything else I've used.