I am an old timer who has had a shop for 50+ years that just purchased an ultrasonic cleaner for the first time. I am very pleased with the job it does, especially on variable caps and other previously hard to clean items. I use a solution of ammonia and dawn detergent for most things. A variable cap comes out "sparkling" clean in just a few minutes even between the plates. My particular ultrasonic has a built-in heater but you could use warm water with a model that does not have that feature. Oh, I cleaned a tone switch assembly off of a zenith 7S the other day and it too came out first class. I would recommend one of these if you have a spare hundred bucks at Christmas.

Hi.

What make, model and source do you have?

Thanks, Fred

Fred: My cleaner is an ebay purchase made by Fisher Scientific and is a model FS20, however, I have noticed that these things are available even at harbor freight tools.
I would recommend one with a built-in heater since it prevents you from having to pe-heat the solution. I used mine last evening to clean some Devilbiss spray gun parts that I use to spray lacquers and it did an amazing job even on the lacquer remnants that remained in the small holes and crevaces. Hope this helps.

It's best to keep your hands out of it while it's running. It tears up the cartilage in the hands, evidently. No big deal with a little exposure but after a while..
We used wicked huge freon-filled ones in the early '80s and I found out the hard way what it can do to connecting tissue. Nobody told me it was a bad idea..

Freon, that must have been very cold, how could you put your hands in that? How did they keep it form just evaporating into the air?

You probably need to re-lube the bearings in those variable caps after cleaning.
Ultra-sonic does a really thorough job!

Rich

You have to watch ammonia. It will shine up brass or copper but will probably etch the metals if you do not take the stuff out soon enough. They have a heated one at work. The catch is that it is a non thermostat controlled one. So if you forget the heater, your solution will practically evaporate or get really hot after awhile. They used some stuff without ammonia in it at work, but it costs about 50$ a gallon. Too rich for me to use in mine. So I took parts to work alot. I suppose you could have a distilled water rinse for the parts that go in the ammonia to neutralize it.

STill haven't found what the best cleaning solution is to get MOLD off of those 50's era knobs when using my ultrasonic. Some plastics react to water, bleach or other cleaners too. There is one type of plastic used by TV makers in the 50's only that really grows white mold. ITs on there really good and refuses to come clean. Open to your ideas. The best way to get it off after an US treatment is to use my fingernails to scrape it. Other methods scratch the plastic.

Mark Oppat
www.oldradioparts.net

Chlorox kills the mold, or at least slows it down. Once the pitting is there, it is permanent.

I have had some luck with pumice or rottonstone and water paste used to scrub with a toothbrush, toothpick for grooves, bit of cotton, or a cotton buffing wheel (gently) on a dremel turning slowly. Once it looks as good as it is going to get, paste wax and buff. Leave it in a damp cellar though, and it'll all grow back in a year. Same more or les applies to ancient bakelite knobs, but there we do the minimum, and mold does not grow on them.

Of course you can always spray the knobs a couple of times and the pitting will go away, and you at least will have the correct shape knobs, if not exactly the right color. Spray the back side too, but stuff the mounting hole and set screw hole and of course remove set screw if it has one. I've used the same Rustoleum sprays I use on chassis on these rotton knobs, let dry a week, and if 10 years is a permanent cure, they survive.

I can always detail by hand, have been doing that for years. Good ideas... but as a knob dealer, I am trying to find something to avoid all the hand work.

Also, I would like to find something to put into my travelling plastic bins I store my knobs in and take out to the shows. Every time I open a lid off the ones with the 50's knobs in them you can really smell the mold.

Mark Oppat
www.oldradioparts.net

We have drifted from tuning cap cleaning to knob cleaning.

If there is more on knobs to discuss, please create a new posting.

Thanks,

Chuck

I prefer a 3% Hydrogen Peroxide dip, less damaging than bleach (Clorox).

I just got my new ultrasonic cleaner and am sorry I did'nt get one years aqgo.I just finished my first variable cap and it came out looking like new.I have a 2.5 liter unit with heater.It's big enough for anything I'm likely to clean.I used a bit of dish washing detergent in hot water.

We had a big freon Cleaner for electronic parts at the Long Beach Naval Shipyard (Now Defunct) that we had just started to use. I was going to be the lead on that machine and was given instructions on running it . Freon liquid is not super cold, it can be used at a room temperature, it feels the same as acetone. It was usually used with a lid on top to keep the evaporation down. The one we had was rather big it was about 5 foot by 5 foot and maybe 3 foot deep.

Anyway during the early 70s Mare Island shipyard in San francisco had a Submarine sink alongside of a pier. That's another whole story of how the sub-safe program got started. Since all the electronics had to be removed and cleaned they confiscated our Ultrasonic cleaner permanently.

To carry on the saga though I went to work later for Tektronix and used an ultrasonic cleaner there to clean finished circuit boards. They had a unique design that heated the freon to boiling point which produced vapors. The vapors condensed on the circuit-cards and dripped off leaving a cleaned set of boards, in the cleaning tank there was a ring of refrigeration coils to help condense the vapors back into liquid also so not as much freon was needed. Of course years later I found out, that when heated freon would form poisonous phosgene gas.

My suggestion for an alternative to liquid cleaners for removing debris for electro/ mechanical parts is to use sand or glass beads in the ultrasonic tank.

After reading these rave reviews I checked out the ebay listings for ultrasonic cleaners and noticed a wide range of prices.
Also, pardon my ignorance, but does one need to remove the variable cap from the chassis and place it into the cleaner? Or, is there a cleaning wand that one holds over the cap?

The variable capacitor should be removed from the chassis and fully immersed in the liquid in the ultrasonic cleaner.

The only caveat is to be very careful with any trimmer caps that are part of the tuning capacitor. The vibration could make the screws back out which could cause the mica insulators to become dislodged and make re-assembly in the proper manner difficult.

That said, me, I wouldn't put a variable cap in an ultrasonic cleaner if it had trimmers on it.

Of course, YMMV.

Check out Harbor Freight. They have a nice cleaner for around 75 bucks. If you get a (plentiful) 20% coupon it is only 55 and no shipping. The only problem is the tank does not curl up over the top edge. The plastic body curls downward to the top of the tank. When emptying the tank, fluid could get into the works. Run a bead of RTV around the seam to prevent that. The RTV does not interfere with the top nor the operation of the unit. Did that with mine and it works great for cleaning tuning caps. The default cleaning cycle is 3 minutes but I usually set it for 6 minutes. Has a heater and digital display also.

No affiliation, etc.

HTH

Bill

I've got one of theose Harbor Freight units. If you look at the exploded view (back page of the owners manual), there is a hidden gasket located under the plastic lip, so any extra "sealing" probably isn't necessary. I admit that, it is sort of annoying to have fluid dripping back into the bowl after it's poured out....a poor design. Kurt

I wouldn't use amonia only because it can permanently damage brass and bronze. Most variable caps arer steel and aluminum, but often have bronze bushings.