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How to cure buzzing chokes/transformers?
How to cure buzzing chokes/transformers?
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Old 29th August 2018, 11:54 PM   #21
esl 63 is offline esl 63
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ultra sonic transducer.... thats tha s**t
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Old 31st August 2018, 04:52 AM   #22
maxhifi is offline maxhifi  Canada
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I wrote to this company about obtaining a small amount, this product looks quite appealing:

http://www.crosslinktech.com/data_sh...xy/CLS9310.pdf
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Old 31st August 2018, 05:06 AM   #23
TonyTecson is offline TonyTecson  Philippines
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How to cure buzzing chokes/transformers?
this is how the Dynaco st70 power traffo looked like, see the wooden wedge used to ensure a tightly stacked core....
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Old 31st August 2018, 10:18 AM   #24
FauxFrench is offline FauxFrench  France
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Quote:
Originally Posted by maxhifi View Post
I wrote to this company about obtaining a small amount, this product looks quite appealing:
http://www.crosslinktech.com/data_sh...xy/CLS9310.pdf
It indeed looks good.
It is a company working with epoxies and polyurethanes. In particular polyurethanes are known to have a strong adhesion. You will need that because your primary concern is to glue the core-plates together such that they remain silent. Secondarily to fill the space in-between the windings to keep them in place. I guess you are repairing 50/60Hz items such that the dielectric properties are less important.

"Note 1" talks about fillers. It starts with "...If a filled resin,...", so I assume this to be a general note. You hardly want fillers in your resin because they tend to clog up the impregnation flow.
Fillers are very useful for embedding of circuits with really thick layers where they prevent cracking. Not suited for impregnation.

For the vibration you can eventually try both options by simply holding the bass speaker or motor with an eccentricity in your hands and feel what is the hardest to hold. The thin ply-wood support sounds like a fine idea as it is very flexible. It will make some noise.

Before impregnation, clean the items well with compressed air. After 50-60 years a lot of dust must have entered. Safety-glasses! Compressed air removes dust and eye-balls with the same enthusiasm.
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Old 31st August 2018, 05:39 PM   #25
maxhifi is offline maxhifi  Canada
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So the response is they make product to order, and need a minimum order of 8 gallons, which have a 3 month shelf life.. not gonna work for me, unfortunately. Will keep looking for a suitable product - shame, as this one has a cure temperature of only 125C, and also, seems to have good electrical and physical properties. You are absolutely correct, strong adhesion is the highest priority. These old RCA theater amplifiers really are my favorite amplifiers, but the buzzing sound the chokes make gets in the way.

I like the idea of cleaning with compressed air, I always blow out old equipment before I bring it into the house. The old transformers also have some loose paint on the outside, I'm not entirely sure if it makes sense to just wire-brush this a bit, or use some kind of solvent. I don't want to contaminate the epoxy with residual solvent or stripper, and I also don't want to damage the coating on the laminations, so I am thinking just a quick wire brushing to get them as clean as I can before dipping.

That Dyna transformer looks pretty good! Is it original from Dynaco?

Last edited by maxhifi; 31st August 2018 at 05:42 PM.
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Old 31st August 2018, 06:54 PM   #26
FauxFrench is offline FauxFrench  France
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I sometimes start with a brushing, using a soft painting brush, if the dust is likely to stick. I finish with the compressed air.
For the loose paint flakes, they are mainly disturbing the aesthetics and too much mechanical handling may make more damage than good. I would remove what I could get off with a dry cloth and accept it is primarily about the electrical functioning.
As you are not sure what are the initial materials used, I would use as little chemicals as possible.
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Old 31st August 2018, 07:05 PM   #27
maxhifi is offline maxhifi  Canada
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Quote:
Originally Posted by FauxFrench View Post
I sometimes start with a brushing, using a soft painting brush, if the dust is likely to stick. I finish with the compressed air.
For the loose paint flakes, they are mainly disturbing the aesthetics and too much mechanical handling may make more damage than good. I would remove what I could get off with a dry cloth and accept it is primarily about the electrical functioning.
As you are not sure what are the initial materials used, I would use as little chemicals as possible.
This is very prudent advice. Function is paramount, I would way rather have ugly transformers which are silent and work perfect, than pretty ones which are compromised from a performance standpoint. I remember when I first ordered Hammond transformers, I thought they were quite ugly, all covered in thick resin. I guess I didn't appreciate at the time, now I understand this actually made them better than some of the nicely painted but not impregnated competition.
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Old 3rd September 2018, 02:50 AM   #28
ilardi is offline ilardi  United States
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About a dozen years ago I tried vacuum impregnation. (I already had a lab grade vacuum pump that I had lucked into). I submerged my coils in a home made “Q-Dope”. At the time I was having hard time finding real Q-Dope so I followed a suggestion to dissolve packing peanuts (expanded polystyrene I believe) in a solvent (I used Xylene). All I can say is that it seemed to work (I don’t quite remember what coil I used this for but it was not a transformer)..In any event, I would expect an appropriate epoxy or polyurethane would have to be better than either real or clone Q-Dope.
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Old 3rd September 2018, 03:16 AM   #29
JMFahey is offline JMFahey  Argentina
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1) as recommended, clean it well

2) dry it. Either in the Sun, under a spot (old style, no LED or anything modern , we want lots of infrared) or in a gas oven set to minimum and with door slightly open or an electrical oven.

3) buy a can of regular, general purpose "synthetic" wood varnish, Marine type does not hurt.
The old type which stinks for hours, seems to attract all dust in the place, remains slightly tacky for hours, the cheapest one.
Not 2 component, Polyurethane, etc.

4) put the warmed up transformer in a fitting container and slowly pour varnish to a side of it, not "on" it, you want to cover it "from below" to make it easier for air to leave.
Then let it soak for at least a couple hours or overnight.

Not as efficient as vacuum impregnation, but not far from it, you trade speed for simplicity and cost.

5) next morning you pull it by the wires, tie it to a broom handle or similar between 2 chairs and let excess drip back into the pot or can.

That general purpose varnish is not wasted, can be used on wood, furniture, whatever .
Let transformer stop dripping, even if it takes a couple hours, who´s in a hurry?

It might take 1 or 2 days for it to stop being tacky, no big deal.

You will KILL buzzing

EDIT: I commercially make transformers, buy specific impregnation type, both air cure and oven cure, but in a pinch wood varnish as I suggest has saved me countless times.
Only problem is that when it warms up, it stinks for the first couple days ... no big deal.
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Last edited by JMFahey; 3rd September 2018 at 03:20 AM.
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Old 3rd September 2018, 03:28 AM   #30
TonyTecson is offline TonyTecson  Philippines
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How to cure buzzing chokes/transformers?
+1 very good advise there...JMFahey......

i was adamant to say "wood varnish", but now that you mentioned it....
except that over here those are more expensive per liter than the electrical grade varnish being sold....

this is how i do mine....the hot manila sun raises temperatures of the traffo by as much as 50*C in summer...
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