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Friday, August 22, 2014

Seized up Variable Capacitor -- Any ideas?


Perhaps in retaliation for all the bad things I've said about regens over the years, the main tuning cap in the old regen I've been working on suddenly went from completely loose to totally stiff.  I can turn it, but it is too tight for the old vernier drive in the regen.  I have replaced it with another cap, but this part was kind of the star of the show, situated as it was several inches above the chassis, connected to the tuning control by a long shaft.   I've tried squirting WD-40 in there -- no joy.  I can't even figure out how to open up the part of the cap where the ball bearings should be. It is an OLD Eddystone from England.   Any ideas? 




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7 comments:

  1. WD-40 is a wonderful product, and has a lot of useful applications, but bearing surfaces are not one of them. Over time WD-40 will gum up and
    bog things down. Try using penetrating oil to loosen up the bearings. It may take a while. Then once free, lube with light weight machine oil such as sewing machine oil or 3 in 1 machine oil.
    Good luck! 73 de Gary, KF6U

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  2. I do agree with the previous comment regarding WD-40. My experience working in an Aerospace R&D lab for many years leads me to consider using either the penetrating oil or electronics grade Isopropanol alcohol. Submerge the parts in a bath of this and place in an ultrasonic cleaner. NOTE: since the IPA is flammable, be careful to not run the unit too long. A half an hour should be good. The IPA will penetrate the annular gap and will act as a lubricant to free up the motion. This should allow for complete disassembly, then the surfaces can be cleaned up to remove any galling that has occurred. This process has served me well when working with sensitive equipment and hardware when galling has happened with both stainless steel, brass & copper parts have been involved.
    VY 73, Alden K6ZU

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  3. I've had good luck "un-siezing" aluminum-on-aluminum shafts using the following method:

    - Get the bushing and shaft as hot as possible with a soldering iron

    - While it is still very hot, smother the joints with a PTFE ("Teflon") based lubricant such as "Super Lube". You can get this at about any local store.

    As the joint cools, it will (hopefully) wick a small amount of the lubricant into it. As it cools, you should be able to (gradually) regain some movement of the capacitor. You may have to repeat this several times.

    I would recommend using ONLY PTFE-based lubricant rather than plain-old oil-based as it will do a better job of de-galling the aluminium-on-aluminium" bushing.

    The above has worked for me several times and never have any of them "re-galled" after doing so. I would also do the above to the capacitors that have *not* yet galled, getting some PTFE into the gap so that it will do its magic before damage is done.

    73

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  4. XE1FV Art Nelson swears by that superlube teflon stuff for the reasons others mention and turned me onto it. Use it in Nissan Sentra, too.

    I used isopropilico alcohol to clean a salvaged cap from a Collins and then the superlube. WD40 is fish oil and leaves a residue that won't, er, due. 73 RBB

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  5. Soak in a sealed tub of kerosene working the shaft daily. After a week the offending detritus will be flushed. Clean, then spray with a dry (PTFE based) lubricant. Dry lubricants attract less dust.
    73.

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  6. Doesn't the "WD" stand for "Water Dispersal" - in other words, it isn't good for lubricating long term. I once sprayed my bicycle chain with WD40 and the next morning all the oil previously there was gone and I had a dry chain.

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  7. Try "PB Blaster". This is the preferred penetrant of automotive mechanics across the country. It really works. Google it. It takes a few minutes to a couple of hours to penetrate and loosen the seized parts. Available at any automotive store or Walmart. Smells weird and stinks. WD-40 is junk, as is Liquid Wrench. I only use WD-40 for removing the gummy residue left behind by adhesive labels. Works well for that.

    As far an oil and anti-corrosion agent for sleeve bearings and metal-on-metal sliding mechanical surfaces in radios, I recommend products suitable or intended for firearms. They are Cleaner/Lubricant/Protectants (CLP). A product called Tri-Flow is quite good. Comes in a spray or drip bottle. Available at any bicycle shop, many gun shops, most any sewing machine shop or Amazon, eBay.

    The best in the CLP class as a firearms CLP would be Eezox but it's not readily available except online. It is a full synthetic oil with killer anti-corrosion additives. It is over-the-top for a variable cap unless, well, you want the best just to have the best.

    A very good firearms lube is Break Free CLP. You can buy it in any gun shop or many Walmart stores in the Sporting (gun) dept. It is also a full synthetic oil, unlike Tri-Flow. Firearms nuts have been using it for decades. Good stuff at a reasonable price and widely available. Use it anywhere you would normally consider WD-40 or 3-IN-ONE Oil.

    A word about what to expect with these CLP-type film lubricants. Remember, they are intended to clean, then lubricate, as well as provide powerful and persistent corrosion inhibitors. The cleaning part is achieved by being thin and containing volatile solvents to penetrate, dissolve, and remove gunk and crud. The product will be thin when initially applied, this is desirable but will cause those expecting a thick, slippery traditional mineral oil to say, "What is this crap?" After several hours to a couple of days, the volatile component will evaporate, leaving a thin film of non-gumming synthetic oil and the corrosion inhibitors. The metal surfaces will have very little oil remaining, this is normal and desirable. You need only a very thin film of stable, non-drying oil to get full lubrication and protection. (Consider this, how much more slippery is an asphalt driveway with 3 inches of ice on it vs. the same surface with 1/64" of ice?) Dirt particles will tend not to stick to the very thin lubricant film, another plus. Finally, the CLP-class products have persistent anti-corrosion additives that straight mineral oils can't compare to.

    If you're a seriously cheap Northeast Yankee, you could buy a quart of Mobil 5W-50 full synthetic motor oil at Walmart and use that. That stuff will beat the pants off WD-40 or 3-IN ONE Oil any day for non-gumming lubrication. Good stuff but lacks the aggressive corrosion inhibitors the CLP products have.

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