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bought a defective cannteena dummy load off ebay

sonoma

sonoma

Sr. Member
Sep 14, 2005
2,105
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oklahoma
I bought a used canntena dummy load that the guy said it just needed oil. when I received it I opened it up and there was paper towels inside it then I saw a brass clamp broken that holds the resister in place. it just had to be the top one. I have searched trying to find one and no luck. a steel clamp will not work with the brass so thought about a 1 inch wide by 4 inch long copper or brass shim stock to replce it with and make my own clamp. that stuff is selling for 17.00 plus for a small piece. I will have to try to find some thing to repair it with.

any one here have any ideas about some thing for a clamp that will not corrode with the original materials?
it just had to be the top clamp and to get to it I will have to pull every thing apart to get to it.
 

The original Heathkit version used Silver Plated Brass strips for clamps...Later versions (clone copies) I think just used Brass.
Steel(rust) or ALM(oxidizes)...not good idea as they breakdown overtime in the Transformer Oil or the lesser effective Mineral Oil...and contaminate the oil. This causes the Flash resistance of the oil to reduce.
So you may have to just grin and bear the cost of the Brass straps.
All the Best
Gary
 
thanks, I did not think of hobby shops. will see if there is one in my area. good idea.
not sure how stainless would react to the original brass.
I was even thinking about trying to put the clamp in position and see if I could solder it back together. long shot at beast. the 2 leads the clamp holds against the resister is spring loaded some so might be able to do that.
the broken part was under the paper towels some one had put in the can to soak up the oil that was left in it. at least thats what it looked like.
 
I watched several of them last night but none are the cantena dummy load, total different animal. most of the ones on you tube are a bunch of resisters and mine just has one large unit for the resister.
 
well after about 1 hour I tore it down and changing position with the 2 clamps worked just fine. now just to get some oil and see how well it works.
thanks for your suggestions guy's.
 
Ebay has a lot of brass flat stock of various thicknesses and widths, most in the $5 to $6 area. I would think it wouldn’t be too difficult to wrap one around a dowel rod for fabrication. If you have a mic tool, measure the thickness of the original. Seeing the original broke, I would be tempted to make yours a little thicker.
 
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FWIW stainless with brass is fine. I have used stainless and brass together outdoors on antennas and it has lasted YEARS without an issue. NEVER mix copper or brass with aluminum however. Galvanic nasties happen rather quickly.
 
after changing the 2 clamps around it is working just fine now so I should be good for some time now.
thanks for all the ideas. after I looked at the assembly instructions I was able to use the broke one in the lower position with the 4 screws that hold it in place it works just fine.
thanks Captain for the info about the stainless if the broken one starts giving me a problem I will go to stainless. just have to find a place with transformer oil if not Heath says you can use mineral oil in the instructions.
I was going to use synthetic motor oil but they claim motor oil is not a good sub for the transformer oil. when these were made synthetic was not being used much from what I remember. mobile 1 was about the only one around for years
 
http://www.mfjenterprises.com/Product.php?productid=MFJ-21

The MFJ-21 is a one gallon container of industrial grade transformer oil. (about $30 gal)
You can use Mineral Oil, however the dielectric properties(Flash Resistance) are not as good as Transformer oil.
I believe the cooling recovery on Mineral is slower also.

The material we used in power houses many times to replace contaminated oil(carbon build-up) in transformers and scrubber units was a Silicon based material (almost slimy) and had a very High Flash Resistance even greater than standard oil. Hi-pot testing it would almost always exceed the normal oil, however it was expensive and a highly controlled material as I recall. So I am sure that was not a product availible without special permits.

CK: Yes I should have noted Stainless steel as used in many transformer bushings and fittings.
However something in the old mind of mine, tells me about the coating or finish as to the grade of stainless whether it is compatible in oil. The "shiny" finish stainless (coating?) I do not recall it's properties. The "Dull (kind'a) Brush" finish is what I recall being the most used in the interior or coming thru to outside of transformers for connections.
So elected not advise in that regard.
Glad you found a "Fix" Sonoma!
All the Best
Gary
 
thanks for the link to the mfj oil. I had forgot about them. I already have a canntena dummy load in use and just bought this one as a backup if ever needed.
the price was not bad other than having to repair it.those little screws and nuts are hard to get a hold of with big hands.my wedding band is a size 13 if that lets you know how big my fingers are.
 
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