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Old 29th April 2012, 11:40 AM   #1
RuiR is offline RuiR  Portugal
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Default Opt laminations isolation

Hi.
Sorry if its a dumb question but i'm a newbie with a problem... accidentally when removing paint from a OPT to earth it accidentally i removed/grinded the paint in the laminations... do i have a problem?



Thanks in advance for any answer.

Rui
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Old 29th April 2012, 12:43 PM   #2
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Actually it is not paint but an oxyde layer (mat gray).
It must have been quite a job to remove that completely; when so the quality of the OPT will be pretty much impaired (eddy currents).
When you just removed the (usually black) paint from the sides of the complete built up transformer I would not bother too much.

Last edited by pieter t; 29th April 2012 at 12:46 PM.
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Old 29th April 2012, 12:56 PM   #3
M Gregg is offline M Gregg  United Kingdom
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I think,

It depends on where and how much can you post a picture?

Then it will be possible to give a better answer.

As above the oxide coating insulates the laminations from each other so its depends on where you have damaged the Tx..

Regards
M. Gregg
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Old 29th April 2012, 01:08 PM   #4
RuiR is offline RuiR  Portugal
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Thanks Pieter and Gregg

I have a picture but i cant upload it from the phone, as soon i arrive home i will upload from the desktop.

Again, thank you
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Old 29th April 2012, 02:03 PM   #5
RuiR is offline RuiR  Portugal
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Quote:
Originally Posted by RuiR View Post
Thanks Pieter and Gregg

I have a picture but i cant upload it from the phone, as soon i arrive home i will upload from the desktop.

Again, thank you

Here it is...


What do you think about it?

Rui
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Old 29th April 2012, 02:42 PM   #6
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This shouldn't be a problem, as you shorted out only a few laminations on the outer edge of the core. No high magnetic flux there, and no large area damaged.

Greetings,
Andreas

EDIT: Remember that some lower quality transformer manufacturers weld the laminations together in two straight lines to save the money for screws and nuts. This shorts all laminations at these two places. Still work ok, though this is not recommended practice if you're building state-of-the-art output transformers.

Last edited by Rundmaus; 29th April 2012 at 02:44 PM.
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Old 29th April 2012, 02:57 PM   #7
RuiR is offline RuiR  Portugal
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Good news

Next time i won't multitasking when building an amp. It cost more time and almost money.

Thank you Andreas

A great sunday to you all.
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Old 29th April 2012, 03:33 PM   #8
nazaroo is offline nazaroo  Canada
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Actually, the welding on transformers such as microwaves is designed to create small eddy currents for safety reasons and RF issues, not to save money on screws.

This practice would be disastrous for audio transformers.

I would strongly suggest you carefully take a knife along the cracks where you have ground them together and shorted them,
and scrap out those cracks just about an 1/8" or less,
and while you are doing this, work in some High Voltage (10,000 volt) insulating lacquer to correct your mistake.

Also, instead of grinding with such a coarse grit, switch to something a hell of a lot finer, like emery paper for finishing jewelry, and wipe down all dust with a damp (but almost dry) cloth.

Somebody warned that some rust-paints may contain iron oxide and be conductive, so I would look for a latex or acrylic primer meant for metal (to seal and prevent rust).
Make sure your primer/paint is non-conductive,
and use it sparingly.
Rather let the High Voltage lacquer get in the cracks between the laminations.

If you can't get lacquer, you might substitute a real mineral oil, which is what some laminations are baked in.
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Old 29th April 2012, 03:36 PM   #9
M Gregg is offline M Gregg  United Kingdom
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As above,

Its not a major concern...However Is this the only damage IE you haven't done the same on the other side?

Believe it or not when it corrodes it will probably be better, LOL

Regards
M. Gregg
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Old 29th April 2012, 04:07 PM   #10
RuiR is offline RuiR  Portugal
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Quote:
If you can't get lacquer, you might substitute a real mineral oil, which is what some laminations are baked in.
Thank you nazaroo.
I don't think i will find 10.000 volt lacquer, the mineral oil approach seems to be the only alternative.


Quote:
Its not a major concern...However Is this the only damage IE you haven't done the same on the other side?
M. Gregg.... Yes it have, much smaller though, between two laminations.



When i think in all the care i had with this project wasted in one minute of pure distraction

Thank you all.
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