Hi All, Does anyone have a reliable method of cleaning variable tuning capacitors? bowler

I have found that its best to leave them alone.
But if its really bad between the plates, a soak with kero then a blast with compressed air.
And re lube.
Avoid pushing cleaning devices or anything between the plates.
Some like everything like new, but I prefer old patina look.
Most can also be completely disassembled also, some easier than others.
JJ

One of the problems I encounter with variable caps, is noisy earthing of the moving plates through the bearings or via the the earthing fork from the vanes to the cap body.

A while back, I had a run of miniature tuning caps with plastic insulating sheets between the vanes breaking away and jamming the cap.

Wayne.

It depends on what the contaminant is, or is it corrosion on the plates? Do note that they are largely Aluminium & alkaline stuff like Caustic Soda (Sodium Hydroxide) will eat it.

If its has trimmers on it, water & such will get under the wafers.

Sometimes the Gang has to be removed. for a general load of stubborn dirt. Aluminium automotive Foaming Wheel Cleaner is good. You may need to hold the chassis sideways, or upside down to keep the wet stuff out of everything else. Circuit board cleaner or alcohol (Metho) will get the water based product out.

Real bad ones may need a bath in Soda Ash (LEC Soda) (Pool soda Ash) (Sodium carbonate) Not Sodium Bi Carbonate aka Baking Soda.

With corrosive mounds which can short. That is where you use need to use card and often emery to try to shift it.

The more brutal method is to burn corrosive mounds off if they won't move. That requires an insulation tester, around 500VDC.and a method of turning the rotor with out zapping yourself. That to identify a bent plate arcing. Do electrically isolate the gang That is best done in dim light so you can see flash overs. If it does not flash over at 500V it won't at operating voltage.

If you think that's scary, the oldies tended to use the HT winding of the power transformer.

So many options

As Johnny says it is best to leave them alone, but if you really need to clean it, I've found the quickest and easiest way to clean a variable condenser removed from the radio is to put it in the dishwasher with the usual dishwasher detergent. This is alkaline and takes off the dirt and brightens up the plating considerably. I take out the ball bearings and adjustment nut before doing this, and clean any grease out of the bearings before going into the dishwasher, and relubricate. (The best grease for this lubrication is moly/teflon brake grease - I find this does not lose its effectivenesseven after extended periods. Expensive, but you don't need much - I still have the same tube bought in the nineties bought to lubricate sqeaky drum brake shoe backing plate bearing on my car at the time.) It comes out of the dishwasher hot so will dry quickly - into the oven at 60C if you like.

You might need to check the effectiveness of the contact between the contact forks and the shaft.

If it is rusty that will need to be treated with rust killer - use one for galvanised iron as it does not attack the plating so much. Paint those areas with a mix of silver paint and gray primer which matches pretty well.

Whatever you do don't put zinc diecast parts in the dishwasher!

Whatever you do don't put zinc diecast parts in the dishwasher!

... or it'll be FINISHed.

Sorry - just a bit of 6AM humour.