Capacitor Cleaning

[ashart]

Gentlemen:

In my restoration of an old AM rig (see www.w8vr.org), I needed to clean a couple of variable caps.  On advice, I borrowed an ultrasonic cleaner, and cleaned the caps in a dilute solution of Palmolive dishwashing detergent and water.

After an hour, I looked at the caps, and all the aluminum parts had turned  a dark gray color.  The caps were electrically ok but cosmetically ruined.  I spoke to 3 different chemists who could not explain the reaction or recommend a reversing reaction.  I very respectfully requested an opinion from a Palmolive chemist, and was tersely informed that my application was not one recommended by Palmolive.  Luckily, I was able to find replacements.

Now, I have two more caps to clean that would be, I think, impossible to replace.  I'm obviously afraid to clean them the same way.

Any PROVEN ideas on what cleaning agents can be safely used on aluminum, (and ceramic and nickel-plated brass) when in an ultrasonic bath?

Tnx de al hart   (al@w8vr,org)

[WA1GFZ]

I take them apart and use scotch brite pads to buff them. Also round sharp edges and flash marks out. Be careful with rebuilding them and torque on ceramic insulators. Snug is enough.

[W7TFO]

You might try putting individual parts through a weak lye bath.  It will slightly etch them back to a bright finish with a little rubbing.  Household bleach might do the trick as well.  Aluminum will react with a base favorably.  Stay away from anything with low pH.  (acids).

Rubber gloves, face shield, common sense.

[W1VD]

At a previous place of employment we had a strong lye bath used for aluminum. An overnight dip of bright aluminum (new chassis for example) would come out looking a terrible dark gray. However, washing away the dark gray film revealed the sought after light gray 'paint looking' finish. Not sure of the details of the chemical reaction was but the new 'finish' was quite durable, even colored and resisted discoloring and corrosion much better than plain aluminum. Once a chassis was mistakenly left in the lye bath over the weekend. Monday morning the chassis was gone - completely dissolved.

Rubber gloves, face shield, common sense.

Common sense...little did we know it was a scarce commodity. Seems there's not much of it around anymore.   

   

[N3DRB The Derb]

I once cooked a 30's National  100 DA in a vat of stewed tomatoes on the stove. It was disgusting looking corroded rails and something you wouldnt buy for a dollar.

It came out of that bath after a water rinse looking brand new. I think I cooked it for about 5 hours. and added maters as needed.

of course it was the citric acid in the tomatoes. Cans of stewed maters are cheap, non toxic, not dangerous in any way, and yer pot will get clean too.

Citric acid powder is available if ya dont wanna cook any maters.  It worked well for me. That cap shone like the sun and it stayed that way.

ultrasonic bath wont really get you much for caps. You need a chemical solution.

[KD6VXI]

You might try putting individual parts through a weak lye bath.  It will slightly etch them back to a bright finish with a little rubbing.  Household bleach might do the trick as well.  Aluminum will react with a base favorably.  Stay away from anything with low pH.  (acids).

Rubber gloves, face shield, common sense.

Local hydroponics / organics store will sell "Ph UP".. Works great.

--Shane

[W1UJR]

Dishwasher, works wonders! Really.

Sorry to hear about the problem Al, sounds like they are still usable, I'd try a very light
bead blast with a moderately abrasive media to bring back the finish.

Back to the dishwasher.

I use Simple Green to spray them down first, and pull them out before the heat cycle.
Dry with a light compressed air blast, and lubricate the bearings on the ends.
I also use DeOxit on the wiper contacts.

Collins 30K output network.






Did the same thing with an National air vairable from an HRO.




I've even been know to wash down complete chassis in the kitchen sink!

[WA1GFZ]

Derb, That is why I like to eat tomatoes. System flush

[N3DRB The Derb]

dirt requires detergents or soap. Al's got a reaction problem. he needs a mild etching solution to etch the stuff off.

I'm tellin ya.... maters. they need a mild mild mild acid bath. the surface has to be etched.

if ya dont wanna do maters....light boil of cream of tartar powder about 3 tablespoons stirred per big pot of water. Like a spaghetti pot.

or go commercial product if ye dont like my home grown. this stuff works too.

http://www.caswellplating.com/aids/albrite.html

[KD6VXI]

dirt requires detergents or soap. Al's got a reaction problem. he needs a mild etching solution to etch the stuff off.

I'm tellin ya.... maters. they need a mild mild mild acid bath. the surface has to be etched.

if ya dont wanna do maters....light boil of cream of tartar powder about 3 tablespoons stirred per big pot of water. Like a spaghetti pot.

I agree, but had THIS problem, using an aluminum "stock pot" (translated, a 55 dollar 5 gallon aluminum bucket for cooking chili and spaghetti sauce in)......:

I made a BIG pot of Spaghetti sauce Saturday morning.  By mid day, it was done.  I was called out of town on a out of state tow (big rig), and ended up showing back up Monday.

The stock pot was completely destroyed.  Pitted to the point of where I wouldn't trust it to not 'leech' into whatever I tried cooking it in.

So, I'd try the maters, it did wonders to my stockpot... BUT, don't let them in too long.

If you don't want to do that, like I said, Ph UP, sold at most gardening centers, etc. will take care of your issue as well.....

ALSO, Ph DOWN, also from the same place, will work BITCHEN as a radiator flush for IRON BLOCK engines!  Will get ALL the crap out of your system about 3 to 5 times faster than "radiator flush' sold at the auto parts stores... Be CAREFUL, it will eat your skin, paint, metal, etc... But, it will also DESTROY the scale inside your engine.

I'd also plan on a replacement of the Water Pump, if you decide to use Ph DOWN as a flush.. It will remove SO much gunk that you'd have to replace it anyway.  While it's off, flush the system with good water, as well.

--Shane

[KD6VXI]

Gentlemen:

In my restoration of an old AM rig (see www.w8vr.org), I needed to clean a couple of variable caps.  On advice, I borrowed an ultrasonic cleaner, and cleaned the caps in a dilute solution of Palmolive dishwashing detergent and water.

After an hour, I looked at the caps, and all the aluminum parts had turned  a dark gray color.  The caps were electrically ok but cosmetically ruined.  I spoke to 3 different chemists who could not explain the reaction or recommend a reversing reaction.  I very respectfully requested an opinion from a Palmolive chemist, and was tersely informed that my application was not one recommended by Palmolive.  Luckily, I was able to find replacements.

Now, I have two more caps to clean that would be, I think, impossible to replace.  I'm obviously afraid to clean them the same way.

Any PROVEN ideas on what cleaning agents can be safely used on aluminum, (and ceramic and nickel-plated brass) when in an ultrasonic bath?

Tnx de al hart   (al@w8vr,org)

Al,

Are you wanting to fix these because they  no longer work, or because you want the aesthetics of "as new"...

--Shane

[WA1GFZ]

I add carrots to my sauce to raise the ph a bit. 15 quart pot on the stove fresh batch tonight. 3 new bags of sauce in the freezer from Monday's batch. I use a stainless steel pot.

[N3DRB The Derb]

yeah, b damn sure you dont cook off all your water in either case. you will ruin your cap.

the cream of tartar is probably the choice - the tartaric acid will work a bit faster, but it's still plenty mild. It's the natural residue left over from fermented grapes, IIRC.

[W3SLK]

I think a duluted solution of either citric or phosphoric acid. If you can't find either in straight form use cheap cola, (Sam's Club). Stay away from high pH stuff. Aluminum don't like it. I also have had success with about 15~60 psi steam. I know not everyone has access to it but it does work.
Gud Luck.

[KM1H]

Take the gray plates, mix them in with plastic beads or walnut shells and tumble them in a machine. Dont walk away as Ive no idea how long it takes in your case. Of course this only works with erector set caps. I can take plates with pecker tracks that pass the thumbnail test and have them as new in 10-15 minutes. Could probably do arced plates by sanding smooth with increasingly finer grades of wet/dry paper and plenty of water. Then tumble. Might be the way to restore some unobtanium plates for those big B&W butterfly caps and other scarce items.

Even a Scotch Brite will reduce the stand off voltage rating, the plates have to be mirror finished. Even pecker tracks that you cant even feel are affected.
Ive experimented with a hi-potter and its a real eye opener. Several 4500V new looking fleamarket caps with just shelf rash fail at 3500-4000V after a soap and water and toohbrush cleaning. Tiny little scratches/abrasion are the culprit. After a tumble they all hold off 5KV plus a bit with a few.

Carl
KM1H

[W1UJR]

Walnut shells are the idea blast media for cleaning/polishing a surface without removal of material. Can also be used in a tumbler. BMW used such to clean intake systems in engines, and they are also utilized to clean aircraft engines.

Pix of results on clock parts:
http://www.fsptime.com/tumbling/index.htm

Vendors:
http://www.kramerindustriesonline.com/blasting-media/walnut-shells.htm

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92155

[N3DRB The Derb]

I've got 2 caps I still need to clean, and I'm gonna make a short video of before and after results with a cream of tartar solution.

[WD8BIL]

Carl has a good idea.
If you or a friend reloads pistol or rifle ammo you can take the caps apart and run'em thru a brass cleaner(tumbler/vibrator).

[KF1Z]

You'll get the best results from either the tumbling idea... or buffing.

Get a chamois or other soft buffing wheel for a bench grinder, or drill (press).

Use a light buffing compound sparingly (aluminum oxide for example)

Buff each piece, then rinse in HOT water, no detergent... dry immediately.

I believe you'll get the best results if you put the time and effort into it, rather than tossing the thing into a bath....

[K9ACT]

We have been tumbling aluminum parts for our MaltMills for 15 years in water, vinegar and detergent and normally get a mirror bright finish.  Some detergents produce a gross gray finish that actually is a surface film that rubs off on your hands.

I have no idea what causes the grunge but every detergent we have used eventually did it and we go back to the supermarket for different samples and find one that does not and use it till they change the formulation again.

The stuff that currently works is Dawn.  The vinegar is critical also. Lie should never be used unless you actually want to etch away the surface but then you need to polish it up again.  Aluminum is actually soluble in lie so left long enough, parts will vanish.  The vinegar assures that there is an acid pH.

I recently disassembled the cap in my 8000 rig and tumbled the plates over night and they not only came out looking like mirrors but all the sharp edges were removed.

The plates for MFJ/Ameritron caps are assembled  the way they come off the punch press and they are exactly what you don't want the edges to look like.

We use 3/8" #6 stainless sheet metal screws as the tumbling media with an ounce each of vinegar and detergent and about half a gallon of water in a one gallon tumbler.

We use the same for brass and silver parts but they do not seem to care what sort of detergent is used.

Jack

[The Slab Bacon]

I once cooked a 30's National  100 DA in a vat of stewed tomatoes on the stove. It was disgusting looking corroded rails and something you wouldnt buy for a dollar.

It came out of that bath after a water rinse looking brand new. I think I cooked it for about 5 hours. and added maters as needed.

but.............How did it taste when it wuz done   

[WBear2GCR]

Using screws as the tumbling media is very very agressive.
I'd opt for something less hard - plastic tumbling media comes to mind for use with a wet tumble.

The walnut shells in a heavier grade can be had from most pet shops as bird cage bedding...fyi.

                           _-_-bear

[K9ACT]

Using screws as the tumbling media is very very agressive.

That's like my wife telling me the flame is too hot under a pot.  They are both time dependent variables.

However, most of what we tumble are castings and it takes at least 4 hours to clean them up and overnight to do a good job.  You simply adjust the time to the task.

Having said that, I should point out that most of the screws have been in there for 15 years and you can barely make out threads, let alone points.  We just add a new box every few years to make up for the ones lost.

I put gold and silver jewelery in this medium overnight and it looks like brand new.  I have put the same gold plated silver pieces in many times and it does not even take off the plating and this is a fairly thing home plating.

Stainless screws are great media, easy cleanup, they do not rust or rot, last forever and are relative cheap.

js

[N3DRB The Derb]

tasted pretty good.....it was the tuning caps for the first HB rig. look how shiny them things are.  Look how good those Johnson neutro caps look.



TO-maters.