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Old 12th February 2012, 12:53 AM   #1
rcbuck is offline rcbuck  United States
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Default How to clean transformer laminations?

I'm rewinding a small power transformer to use as an audio transformer. I have removed all the laminations. The transformer had been dipped in wax when it was made.

Does anyone know of a way to remove the wax from the laminations? This will help in being able to put all the laminations back without having to force and possibly damage the last few.

I placed all the laminations on a sheet of metal and heated them with a propane torch hoping to burn the wax away. That wasn't very successful as it just seemed to level the wax but not burn it away. The fact that wax is now smooth on the laminations may be sufficient to allow easy re-assembly. But removing it if possible would be better.
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Old 12th February 2012, 01:05 AM   #2
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Don't think there are any solvents to cut wax. I'd dip the laminations in boiling water then wipe on paper towels while still hot.
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Old 12th February 2012, 01:21 AM   #3
AJT is offline AJT  Philippines
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lacquer thinner bath....more work but scraping with a spatula helps
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Last edited by AJT; 12th February 2012 at 01:24 AM.
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Old 12th February 2012, 01:34 AM   #4
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A little research shows any "non-polar" solvent. Mineral spirits, naptha, turpentine, brake cleaner, xylene or possibly kerosene. I'd still go with hot dunk and wipe.
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Old 12th February 2012, 01:40 AM   #5
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Dont remove the wax !!!!
The wax is meant to insulate one lamination from the next to stop eddy currents !!!
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Old 12th February 2012, 01:52 AM   #6
AJT is offline AJT  Philippines
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you can't remove it 100% anyway....
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Old 12th February 2012, 02:15 AM   #7
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Sounds like you have a Hammond transformer and that would be more like glue and wax together.

Wax is not meant to insulate one lamination from the other. Insulating laminations would not stop eddy currents it would cause them. The old TV transmitter plate voltage transformers would have a nice long bead welded along the top of the laminations to keep such eddy currents from forming if corrosion set in.

I'd suggest not bothering to try to get an EI core power transformer to become an audio transformer unless you really want the experience. Cheap toroidal core power transformers actually have good audio bandwidth performance and would be easy to drop in. Just observe the ratio between input and output. I once listened to a Matrix amp which had been built using only about $120 worth of parts and it used cheap toroidal core power transformers for output transformers. It sounded much better than one could have imagined it would.
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Old 12th February 2012, 02:20 AM   #8
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Quote:
Originally Posted by YouAgain View Post
Wax is not meant to insulate one lamination from the other. Insulating laminations would not stop eddy currents it would cause them..
Taken from Wikipedia.

Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores.
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Old 12th February 2012, 02:33 AM   #9
rcbuck is offline rcbuck  United States
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I will try the dip and wipe. I don't need to remove all the wax, just enough to make re-assembly easier.

This is not a transformer designed for high quality. I am making a test transformer for a 70 volt system at 35 watts. Input will be 40 watts at 6.5 ohms. I figured 5 watts of transformer loss. The frequency range will be from 200 Hz to about 5 KHz. I did all the winding calculations based on a low frequency of 200 Hz.

It was a cheap Chinese 60 watt power transformer. As a result, the size of the core is larger than needed for 40 watts of audio with a low frequency of 200 Hz. Once I have it re-assembled I will drive it with a 1000 Hz tone. If I hear the core singing I will heat the transformer in the over at 350 for a couple of hours which should melt enough of the remaining wax to quieten it down.
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Old 12th February 2012, 02:50 AM   #10
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Hi Nigel, Sounds like both you and me and Wikipedia are not 100% accurate but that's no surprise. It's all interesting. I've seen power transformers with rusty laminations that run very hot because of eddy currents compared to new ones of the same type that run cool. I've never seen anyone put anything between laminations and I expect that that would result in heat from eddy currents and lack of efficiency.
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