how to clean air variable capacitors - dirt on plates

[Opcom]

So the time is coming for starting on the frankentuna..

Several nice beefus caps, but the otherwise good aluminum plates have the grime of the ages on them and have a gray-brown dirty appearance, and I can't get in there with any kind of brush or rag.. I'm not sure ignoring this and relying on "RF cleaning" is an acceptable method!

The picture is an example of how filthy these are. It's dirtier than it looks, it is not just dust that could be blown off with air; it seems to be on there pretty good.

What can I do to clean these things? (I do not have a dishwasher)

[W1EUJ]

Hot water, soap, foam brush. Airdry by the hot water heater/boiler for a day, then oil.

[W3SLK]

Hmmmm, I've had good luck using CIP-200 and water, (about 25% strength.) About 15 minutes and a good flushing with water. Also, 1 part ammonia, 3 parts water works good and is the typical solution for cleaning jewelry, (your jeweler will tell you it some high price stuff ). You can use some of your different metal cleaners in a spray bottle but they have a tendancy to streak. Go with something you can dunk in a bucket. Have 2 buckets, one for cleaning and one for rinse. Gud Luck in the Corntest

[VE3GZB]

I used to have one old salvaged variable capacitor from a late 1920s/early30s AC powered radio I had as a teenager, and this capacitor was horribly rusty! The plates, the end plates, you name it!

I used that Rust Remover you can buy for your car (some kind of acid). It cleaned it up right quick! Then just rinse with cold water and dry with a hair dryer!

[w4bfs]

yessir Patrick ... I have found that I indeed have variable capacity, depending upon excitation! ...73 ...beefus

[KD3CN]

I asked for advice on this a while back.  Got lots of good info, and entertainment to boot!

http://amfone.net/Amforum/index.php?topic=10285.0

73, Karl

[WA1GFZ]

I've taken them all apart and cleaned each part. This way you can buff out the flash over marks. Dish washer soap in a pail of hot water works well.

[WBear2GCR]

a run through the lowly dishwasher with dishwasher detergent does wonders for aluminum and ceramic...

after that you can touch it up and relube as needed...

              _-_-bear

oh... get thee a dishwasher - they're free outside of most larger appliance stores around here (in the back) not much ever really goes wrong with them - just grab a few of the same brand and almost all the parts interchange! 

the alternative is to soak and agitate them in a bucket (plastic) with very hot water and a good dose of liquido dishwashero detergento... about an hour or so ought to make it perfectly wonderful. You will loose the decal though... unless you don't dunk that part...

Also the alkaline cleaners (Mean Green, Thunderbolt, and "degreasers"/floor strippers) will clean up aluminum and the ceramic as well... spray on, rinse under hot water, repeat as needed... pretty good results that way too...

[k7yoo]

I am sure there are a gazillion ways to clean variable caps--but the easiest and cheapest is Scrubbing Bubbles. I usually put the cap (or radio) right in the bathtub or shower, foam it, let it sit for a few minutes, and rinse with hot water. You can use a hair dryer or set it in front of the heat register to dry. Relube and away you go. What's great about this is that your shower or tub gets cleaned at the same time. If you want to really be efficient the cap can replace your regular rubber ducky and you can be entertained and clean at the same time!
Seriously though, I have used this stuff to clean all of my B'cast xmitters, radios, etc. Bare metal brightens right up. DO NOT let it stand on paint though--it can streak and EFJ paint runs right off.

[k4kyv]

I would be careful about aggressively washing the ceramic parts too much, such as by running through a dishwasher.  I distinctly recall warnings from EF Johnson or National (maybe both), years ago, that the unglazed ceramic insulation in their rf components is coated with some kind of moisture proofing oil or wax, and that solvents or too much scrubbing may remove that protective coating.  Unglazed ceramic is hygroscopic, meaning that it absorbs moisture from the air, and this degrades its insulative qualities, possibly leading to failures.  First it arcs over, which then leaves carbon tracks that are impossible to remove, and sometimes the ceramic actually cracks.

I would disassemble the capacitor, cleanse the ceramic with a cloth wetted with a mild detergent solution, then clean and buff the plates in a separate solution. 

I vaguely recall that the protective coating is some sort of silicone product.

[WA1GFZ]

Gee I wonder if tile grout sealer would work???

[k7yoo]

I haven't experienced any problems with cleaned components and have applied this treatment to at least 6 KW matchboxes and innumerable high power tank components. Most capacitor and switch parts are unglazed (unlike standoffs), and I have seen few with any coating. My guess is that most of the junk we are saving is so old that the benefit of cleaning the crud off far outweighs any other factors.  Carbon tracked switches can be saved by glass beading--I have saved at least half a dozen high power switches this way. I do agree that a sealer would be a nice touch. A light coating of thinned Q dope or even Conformal coating would work well. Keep it thin to permeate the ceramic. I haven't tried grout sealer but the sealing properties may be beneficial--it is also very thin. I am not sure about the dielectrics though--should be OK.

[k3zrf]

And if all this advice doesn't work put 'em on the firing range like our northwest friends!

[KL7OF]

And if all this advice doesn't work put 'em on the firing range like our northwest friends!

     

Yes    Yes...The tube shoot is this weekend....Look for us on 75 and 160 ...Pictures will follow...
STEVE

[Opcom]

evil, shooting tubes.. even TV set tubes..

[k7yoo]

I might be there next year Steve. I have two large boxes saved up for the occasion-4-1000's, 4-400's, 250 th's, and more!

Skip

[k3zrf]

Yes    Yes...The tube shoot is this weekend....Look for us on 75 and 160 ...Pictures will follow...
STEVE

That sounds like a lot of fun. Seems this time of year I think about you and the event.

We used to shoot at a Flying"A" horse sign behind DUQ's with 12ga slugs years ago.

The sign was on the ground, not at the gas station

[w8khk]

I might be there next year Steve. I have two large boxes saved up for the occasion-4-1000's, 4-400's, 250 th's, and more!

Skip

These dead tubes make very nice lamp bases...  Shame to blast them to pieces.  Need a sign to shoot at?  The local TARGET store seems to fit the bill....

[Steve - WB3HUZ]

I have some 300Bs if you want them.

I might be there next year Steve. I have two large boxes saved up for the occasion-4-1000's, 4-400's, 250 th's, and more!

Skip

[K1DEU]

No dishwasher; Car Wash time !

[k4kyv]

I have some 300Bs if you want them.

Hope they are crapped out.  Otherwise, the audiophools would cry their eyes out.  Actually, they would make better class-B driver tubes than 2A3's, so save them if they are still good.  Of course, a good 300B would fetch enough on ePay to buy a brand new four-by-one.

[WA1HZK]

I run all that stuff through the dishwasher. Put it in the oven at the lowest temp possible to dry.
Works Pissa.
Keith

[flintstone mop]

We always seem to forget the Italian way to clean capacitor plates.........and that is a big pan that you can immerse the capacitor completely in tomato sauce and boil in this sauce for a couple of hours. The plates look like new. And then the usual rinsing and drying in a warm oven for a couple of hours.
THEN invite your friends over for one helluva Italian meal re-using this sauce.
The first paragraph is true.........the last sentence is not.

G'day

fred

[WU2D]

Let WA1GFZ do an AQL test. If it passes HiPot, do nothing - install.