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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 27th Apr 2009, 8:05 pm   #1
Martin G7MRV
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Default cleaning tuning capacitors

Hi All,

can anyone give me some sensible advice on cleaning up tuning capacitors? Ive one that i have salvaged, ive swept out the vanes with a soft brush, but its still a little dirty, i'd like to clean it up better before reusing it

ive seen all sorts of chemical cleaners mentioned on other sites but these all seem to be american


Martin
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Old 27th Apr 2009, 8:10 pm   #2
Sean Williams
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Default Re: cleaning tuning capacitors

Bung it in a dishwasher (check the XYL is out first)

Been doing it for years, and results are impressive!

Sean
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Old 27th Apr 2009, 8:11 pm   #3
Martin G7MRV
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Default Re: cleaning tuning capacitors

thats something ive heard, any hints on settings?
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Old 27th Apr 2009, 8:21 pm   #4
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Default Re: cleaning tuning capacitors

For the standard aluminium tuning gangs, I slosh them around in a bowl of hot water with some ordinary washing powder, rinse and dry thoroughly and re-oil the bearings, they usually come up nicely .

Regards, Mick.

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Old 27th Apr 2009, 8:29 pm   #5
Sean Williams
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Default Re: cleaning tuning capacitors

Normally just use a hot wash, then as soon as the cycle finishes, pull them out, so the heat in them dries them off
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Old 27th Apr 2009, 9:36 pm   #6
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Default Re: cleaning tuning capacitors

Like Sean, I recommend the dishwasher too. Can I add to his advice that I prefer to use the top (least aggressive) part of the dishwasher, and that works fine. And as Mickjjo points out you MUST remember to lubricate the bearings afterwards.
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Old 27th Apr 2009, 11:05 pm   #7
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Default Re: cleaning tuning capacitors

If you can dismantle it without unsoldering anything then I would do that. If it is brass then you could polish the vanes after the washing machine. A lollipop stick may fit nicely between them depending on how miniature the thing is. If it is aluminium don`t leave it too long in the washing machine as the detergent may attack the aluminium..
Pat G3IKR
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Old 28th Apr 2009, 12:04 am   #8
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Lightbulb Re: cleaning tuning capacitors

Interesting Thread.

Washing powder contains caustic soda (sodium hydroxide, NaOH) - albeit in a dilute form. Caustic soda will attack aluminium - I frequently use it (diluted with water) in the kitchen to remove stubborn baked-on grease from aluminium cooking trays that have been used in the oven. Since this chemical is not that difficult to obtain 'over the counter' as 'soda crystals', perhaps a solution of same in a plastic washing-up bowl will do the same thing - without using the washing-machine, etc.

A few words of caution: there will be noxious fumes given off, the density dependant on the strength of the solution. Use a face mask to protect your lungs; plastic / rubber gloves to protect your fingers. Having a window open nearby is also a good idea. And don't splash the solution in your eyes! Wear goggles.

Al. / Skywave.
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Old 28th Apr 2009, 12:37 am   #9
Martin G7MRV
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Default Re: cleaning tuning capacitors

A good few ideas there.

Im not sure i will have to go as strong as Sodium Hydroxide, might look a bit odd to the neighbours if im stood outside in my old S10 respirator swirling radio parts in a bucket
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Old 28th Apr 2009, 7:32 am   #10
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Default Re: cleaning tuning capacitors

I'm with the dishwasher folk!

I dismantle the cap first, though, and remove the steel balls. Advisable to count the threads on the screw so the spacing (and therefore capacitance) are the same, but prepare for realignment afterwards.

Use thick (water-pump) grease on the bearings.

The advantage of using the dishwasher as opposed to just washing it in a bowl is that the high-pressure spray generated that really does clean everything.
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Old 28th Apr 2009, 7:47 am   #11
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Default Re: cleaning tuning capacitors

I'd go for the dishwasher too. But first, put a few pieces of aluminium through (even a small plate wrapped in aluminium cooking foil would do) just to check the detergent doesn't attack aluminium.

As has been said, caustic sode (sodium hydroxide) attacks aluminium fairly quickly. Washing soda (sodium carbonate) will, albeit slowly - and this is a likely ingredient of dishwasher tablets.
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Old 28th Apr 2009, 8:03 am   #12
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Default Re: cleaning tuning capacitors

It's important to ensure that any cleaning chemicals are washed off at the end. Dishwashers do a rinse cycle for that.

Any other method should be followed by thorough rinsing e.g. in distilled water. Domestic cleaners are usually alkaline and so the aluminium parts will be slightly etched as a result. They also often contain salt which if not washed off will deal with the steel parts in time.

I usually clean variable capacitors using a degreasing gun blowing a solvent like meths or IPA.
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Old 28th Apr 2009, 8:19 am   #13
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Default Re: cleaning tuning capacitors

Can I ask a simple question? Why?
The object of the exercise should be that it works properly. Anything else is akin to the people who religiously clean the engine of their car, get the manifolds and rocker chromed and then leave the bonnet open so everyone else can see.
If it's dusty then blow and brush.
If it's greasy wash it in , say, meths.
Certainly relubricate, adjust if necesary and make sure the moving contacts are clean.
If it's corroded then the more exotic methods quoted may well be necesary, but I guess at that stage you're in the lap of the Gods anyway.
Alan
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Old 28th Apr 2009, 8:36 am   #14
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Default Re: cleaning tuning capacitors

Quote:
Originally Posted by AlanBeckett View Post
Can I ask a simple question? Why?
To make them work properly!

I wouldn't ever touch them if they were working OK, but excessive dirt between the vanes can change the capacitance, or worse! Past experience suggests that attempts to improve them often make them worse so I consider this to be a last ditch.

I guess some people also like their sets to look brand new.
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Old 28th Apr 2009, 9:41 am   #15
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Arrow Re: cleaning tuning capacitors

Quote:
Originally Posted by AlanBeckett View Post
Can I ask a simple question? Why?

The object of the exercise should be that it works properly. Anything else is akin to the people who religiously clean the engine of their car, get the manifolds and rocker chromed and then leave the bonnet open so everyone else can see.

Alan
With all due respect Alan, I think the simple answer to your question "Why" is that many people at this Forum are here because they want to 'restore' their sets in addition to getting them 'working properly', where 'restore' = a condition, appearance & performance as when the set was first manufactured.

That would appear to be the 'object of the exercise', although I appreciate that there are degrees of 'restoration & repair' that will vary according to any particular individual's wants, needs and opinions.

Al. / Skywave.
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Old 28th Apr 2009, 10:14 am   #16
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Default Re: cleaning tuning capacitors

Well, I like the chassis of my radios to be things of beauty, also, and I give my tuning capacitors a good seeing-to. Having said that, although I supported the idea of a dishwasher in my earlier post, I've not actually done this because the dishwasher in my house is me!

The last variable capacitor I cleaned was of Polar manufacture, rivetted and soldered together, and I didn't disturb these. So, I cleaned everything with white spirit and a soft paint brush. I find white spirit in a pump-action spray bottle, ex-bathroom cleaner, is really useful as you can put a bit of force behind the spray.

After cleaning and thoroughly drying (2 days), I re-lubricated the bearings using a mixture of motor grease and Moly-slip, thinned down with enough paraffin so that I could squirt it using a hypodermic syringe and flexible tube, putting it exactly where I wanted it, a good blob between each ball. The idea is that the paraffin will inevitable evaporate but the grease will be left behind. There is a wire spring to give good contact with the rotor, and this I left unlubricated (although thinking about it some switch contact grease would not come amiss here).
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Old 28th Apr 2009, 10:18 am   #17
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Default Re: cleaning tuning capacitors

Al,
This of course gets back to the 'how much restoration' debate, so we'd better agree to differ before we're chopped off
Alan
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Old 28th Apr 2009, 11:16 am   #18
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Default Re: cleaning tuning capacitors

When a tuning capacitor is really greasy and filthy, I run it through the parts washer for an hour or so (using Swarfega dilute degreaser) followed by a "gentle" blast of compressed air and then a re-lube.
Neil
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Old 28th Apr 2009, 11:28 am   #19
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Default Re: cleaning tuning capacitors

Quote:
Originally Posted by GMB View Post
It's important to ensure that any cleaning chemicals are washed off at the end. Dishwashers do a rinse cycle for that.
.
Also remember that the "rinse-aid" is dispensed in the final rinse.
I don't know what chemicals are in that.

Frank
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Old 28th Apr 2009, 1:26 pm   #20
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Default Re: cleaning tuning capacitors

Quote:
Can I ask a simple question? Why?
It is generally reckoned among radio amateurs that a clean variable capacitor leads to a more stable oscillator. I guess the dielectric constant of dirt varies considerably with humidity and temperature. Not really a problem with domestic sets, except on higher SW frequencies. Done badly (e.g. distorted vanes, wobbly bearings), cleaning could make things worse so I would leave well alone on a domestic set apart from a quick blow or a very soft brush to get the loose stuff off.
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