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Old 28th Nov 2022, 11:47 pm   #1
AdrianH
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Default Any way to make the variable tuning capacitors shine?

Well not necessarily shine, but to remove the oxide/crud layer from them so they at least look presentable. Talking of the tuning caps in old valve radios here.

Any dip/solution that can be used on manly the steel sections to make them gleam again, up to now a small wire brush is being used and while it works, can mean a lot of careful scrubbing.

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Old 29th Nov 2022, 12:05 am   #2
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Default Re: Any way to make the variable tuning capacitors shine?

Ive not seen many steel variable caps. Oh, the frame is usually steel ( NOT Philips ) but the capacitors is usually aluminium and the shaft is always brass.

They are note easy to clean in my experience.

Joe
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Old 29th Nov 2022, 12:12 am   #3
AdrianH
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Default Re: Any way to make the variable tuning capacitors shine?

Yes should have said that most of them seem to be steel frames, aluminium fins and brass shafts as you say Joe, just worried some time I am going to trash the aluminium fins by accident.

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Old 29th Nov 2022, 12:54 am   #4
Bazz4CQJ
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Default Re: Any way to make the variable tuning capacitors shine?

I cleaned up a pretty old tuning cap very nicely last week in my ultrasonic bath.
I used an additive supplied to clean carburettors.

Some caution is needed when using aqueous solutions to clean components comprised of different types of metal as electrochemical reactions can occur and I've see strange (and bad) things happen.

So, these days I start with a solution at probably no more than 30'C and I keep a close eye on the component. Often, just a few minutes is adequate.

If you don't have an ultrasonic, not sure what advice to give except stay away from anything with chloride in it, e.g. bleach and washing up liquid. Chloride initiates corrosion.

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Old 29th Nov 2022, 1:06 am   #5
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Default Re: Any way to make the variable tuning capacitors shine?

Oh I do have a small jewellery type ultrasonic bath somewhere, I could always try to do half then flip over.

What is the additive you use, mixed with water I assume. I nearly melted the ultrasonic bath once when I added acetone in the tub

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Old 29th Nov 2022, 1:21 am   #6
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Default Re: Any way to make the variable tuning capacitors shine?

Another problem I have found is that although the steel frames are plated and somewhat resistive to corrosion, the aluminium can be washed in water BUT, the ballbearing race in the control end. and the single ball at the floating end are VERY conducive to rust.
That makes the capacitor "clunky " to rotate. To some degree, a quck application of sewing macine oil, or your favorite grease helps, but once damaged a ball bearings surface is not repairable.

Joe
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Old 29th Nov 2022, 11:27 am   #7
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Default Re: Any way to make the variable tuning capacitors shine?

I have had good results using washing powder and very hot water in a plastic bowl you only need a small amount of powder , a pair of pliers to agitate the item for a few minutes then rinse with hot water ,a quick squirt of WD 40 on the moving parts ,after drying on the convection heater oil the bearings .
I also use this method for cleaning the wiring and valve bases when restoring jukebox amps it works a treat. Mick.
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Old 29th Nov 2022, 12:23 pm   #8
Al (astral highway)
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Default Re: Any way to make the variable tuning capacitors shine?

Dishwasher is one way. Detergent can leave a strange patina on the aluminum oxide layer, but who's going to be looking?

Ultrasonic bath is good, too. I add a drop of washing up liquid as a wetting agent. Brand I use doesn't introduce the problem Bazz mentions in #4
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Old 29th Nov 2022, 12:53 pm   #9
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Default Re: Any way to make the variable tuning capacitors shine?

Adrian, is your jewellery bath ultrasonic? My wife has one, but it is like a motor arrangement that agitates the liquid. Not ultrasonic.
I have an ancient ultrasonic cleaner, the tank is about 6 inch cube.
Powered by a single 805 triode. The value of that must be more than the entire machine.
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Old 29th Nov 2022, 1:26 pm   #10
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Default Re: Any way to make the variable tuning capacitors shine?

yes the bath is ultrasonic at 42,000 Hz not very powerful with a total power consumption of 50 Watts.

Bought off Ebay some years ago a James 7000S, just had to find it again.

I have clean one cap in a solution of hot water and washing powder and that has come up a lot better looking then previous, so now trying the same in the ultrasonic bath with another one.

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Old 29th Nov 2022, 1:48 pm   #11
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Default Re: Any way to make the variable tuning capacitors shine?

Air spaced variables, e.g. Jackson, Eddystone, have silver plated brass plates and these
are easily cleaned by immersion in jewellery cleaners, or even in extreme cases Harpic
which is mild HCl. Rinsing, drying and relubricating restore to as new condition.
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Old 1st Dec 2022, 4:13 am   #12
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Default Re: Any way to make the variable tuning capacitors shine?

This is the additive I used for ultrasonic cleaning of the condenser https://www.allendale-ultrasonics.co...cleaning-fluid.

As it is intended for carbs (ali and brass), that's not a bad start for variables.

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Old 1st Dec 2022, 12:12 pm   #13
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Default Re: Any way to make the variable tuning capacitors shine?

Thanks for that, I have ordered some to try.

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Old 1st Dec 2022, 7:12 pm   #14
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Default Re: Any way to make the variable tuning capacitors shine?

People who know about ultrasonic cleaning always tell me that, to get best results, you should de-gas the solution before putting the component in. That is to say, switch the cleaner on for ~10 minutes before you put the part in.

I don't always do that, but with something like a condenser, I think we need to get it and out in the minimum time (to be on the safe side) and so I would de-gas.

I did an old twin gang that came out a battery-valve portable from the 60's, it went in looking tired but came out almost like new after just a ~5 minutes? I think I smeared Vaseline thinly all over the steel part, and then lubed the ball-race. It's going in to my "QST" receiver .

For more general cleaning, I used to use a product called Decon 90 throughout my working life, but that is somewhat alkaline and suits things like stainless steel very well. The Allendale stuff has worked well on carbs and condensers... which could be the title of my autobiography .

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Old 1st Dec 2022, 8:02 pm   #15
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Default Re: Any way to make the variable tuning capacitors shine?

If using more volatile solvents or nastier ones, the trick is to put the solvent in a glass beaker and put the beaker into the tank, suspended clear of the tank base.
Use warm water with washing up liquid in the tank and de-gas

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Old 1st Dec 2022, 8:28 pm   #16
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Default Re: Any way to make the variable tuning capacitors shine?

Quote:
Originally Posted by Ed_Dinning View Post
Use warm water with washing up liquid in the tank and de-gas
Ed
"washing up liquid" only if you are 100% sure there is no chloride in it.
The very deep pressed-steel baths in ultrasonic cleaners will be exceptional thin in the corners and very susceptible to chloride-induced corrosion which may show up first as pin holes.

I think this is an area where sticking with the manufacturer's instructions is very much the way to go. My lab-grade bath is 25 years old now and will still punch holes in aluminium foil.

B
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Old 2nd Dec 2022, 5:01 am   #17
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Default Re: Any way to make the variable tuning capacitors shine?

It depends on the tuning capacitor. Some you can unbolt all the plates and hit 'em with metal polish and elbow grease.

For non-dismantleable ones Peter Martin (G3PDM) wrote up his method of cleaning them in in his article for his HF receiver, published by RSGB in Radcom/Bulletin and it also went in the RSGB Radio Communication Handbook late sixties edition. He was interested more in stability than shine, but went down the ultrasonics route.

David
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Old 2nd Dec 2022, 6:55 am   #18
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Default Re: Any way to make the variable tuning capacitors shine?

I have seen those David,
5/8" Whitworth thread with a torque of 75 foot pounds per "leafe ". Two bolts top, and two bolts on the bottom of each aluminium fixed plate.

I have seen the main fixed vanes screwed into the frame, in their own smaller frame, but there is NO WAY to dissemble them.
( Like he said, " Do not dissemble " )

Did I read this correctly??.

With respect,

Joe
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Old 2nd Dec 2022, 12:36 pm   #19
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Default Re: Any way to make the variable tuning capacitors shine?

I have a big ATU sized capacitor 250pf + 250pf. Rotor vanes and stator vanes all removable and reassemble-able. Sized so that in only one rotation, it could slice an entire cucumber.

Took it apart, polished the plates and rounded their edges to put the flashover voltage up. It was going to tune a big amplifier up at the local club.

Shiny!

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Old 2nd Dec 2022, 3:56 pm   #20
Bazz4CQJ
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Default Re: Any way to make the variable tuning capacitors shine?

Quote:
Originally Posted by Radio Wrangler View Post
For non-dismantleable ones Peter Martin (G3PDM) wrote up his method of cleaning them in in his article for his HF receiver, published by RSGB in Radcom/Bulletin and it also went in the RSGB Radio Communication Handbook late sixties edition. He was interested more in stability than shine, but went down the ultrasonics route.

David
Can you give any more detail on that David? I have the 1968 Handbook but have never spotted it.

A significant thing to remember was the widespread use of the Freon type (CFC) solvents that used to occur in sonic baths in the past. Those solvents were very high density (very good in sonics) and were exceptional degreasing agents. At the time when they were rapidly phased out, many though it would be impossible to find anything as good or better, but the chemists soon came up with additives for use with water that were very good. Of course, those are the products we have to use today, though some countries are still producing and discharging CFC's in to the atmosphere .

The two-gang I cleaned recently was a very basic unit, with no adjustment or removal possible, but still a nice movement and fine for Rx use.

B
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