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Old 18th June 2017, 10:25 AM   #1
GUNFU is offline GUNFU  Russian Federation
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Default Electrostatic screen in OPT. Is there any benefit?

Hi guys!

In the 1950s and 1960s, an electrostatic copper foil shield between the transformer sections was widely used in output transformers. Now do not apply. And the geometry of sectioning has not changed much. I propose to discuss, is there benefit from this screen in the output transformers?
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Old 18th June 2017, 11:22 AM   #2
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Are you sure that was in the output transformers?

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Old 18th June 2017, 11:27 AM   #3
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It is unusual to use a screen unless in a mains transformer and the sole benefit of an electrostatic screen, in a mains transformer, is obvious.
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Old 18th June 2017, 12:29 PM   #4
GUNFU is offline GUNFU  Russian Federation
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Quote:
Originally Posted by Bas Horneman View Post
Are you sure that was in the output transformers?

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Yes. This article is from the journal for 1958. It has an amplifier on 807 tubes. The author is an old Jew from Odessa, a very authoritative author. A bit later, I am modifying the US patent from 1954 where also electrostatic screens are used in the output transformer. And the author is an American of Russian origin.

Unfortunately they both wrote and did not specify why the electrostatic screens in the output transformer, only mentioned that they are.

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Old 18th June 2017, 12:35 PM   #5
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Quote:
Originally Posted by JonSnell Electronic View Post
It is unusual to use a screen unless in a mains transformer and the sole benefit of an electrostatic screen, in a mains transformer, is obvious.
Audio amplifier system
US 2924780 A
Priority Date
Jun 30, 1954
The inventors of the invention
Bereskin Alexander B
The original patent owner
Baldwin Piano Co
https://www.google.com/patents/US2924780
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Old 18th June 2017, 12:37 PM   #6
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Not sure this implies "widely used" as your original post suggests. Might there be a few out there? Sure.
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Old 18th June 2017, 12:46 PM   #7
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Quote:
Originally Posted by zigzagflux View Post
Not sure this implies "widely used" as your original post suggests. Might there be a few out there? Sure.
Nevertheless, they used to be used and probably not from the whims or whims of the authors. In both these old transformers there are electrostatic screens, without mentioning the destination, as if this goes without saying. The power transformer also has a screen. I doubt to filter this interference from the network out again.
Although I read the patent carefully, maybe I missed something, in the description of the details, because I'm not a native speaker of English.

Last edited by GUNFU; 18th June 2017 at 12:49 PM.
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Old 18th June 2017, 01:46 PM   #8
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Some years ago i disassembled an old Siemens OPT used in a 100 watt power amp with 4 EL34 , and there was inside at least 10 electrostatic copper foil between all the sections of this OPT connected to ground.
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Old 18th June 2017, 02:15 PM   #9
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You can find and show here the circuit of this amplifier in order to better understand its features and why they used these electrostatic screen in OPT?
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Old 18th June 2017, 02:20 PM   #10
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The patent speaks of a novel negative feedback system, which is common knowledge but the use of the screen, acts as a shorted turn, reducing the need for an air gap to allow the field to collapse easier than if there was no air gap. Plus adding to the insulation to avoid flash over, very rare on output transformers.
As, and judging by the dates from 1927, there has been ample time to develop this, if it was indeed, successful.
I would say that it was not as good as described, much like the majority of patents, as if it were, it would be widely used and is not.
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