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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 27th Nov 2020, 4:59 pm   #1
Ian - G4JQT
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Default Ekco A22 V2 suppressor grid

Trader Sheet 768 and the Ekco Data sheet, all show p5 screen grid on V2 EF39 returned directly to its cathode, yet in two out of three A22s I've worked on p5 goes straight to chassis.

Trader is usually pretty good at describing production modifications but this particular one isn't mentioned.

I'm assuming the attached image shows how it was originally designed, or maybe a drawing error? In any case, can anyone think of a reason a change may have been made, or what difference it would make?

Thanks.

Ian
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Old 27th Nov 2020, 6:15 pm   #2
AC/HL
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Default Re: Ekco A22 V2 suppressor grid

That's the suppressor grid, there to remove the tetrode kink. It just needs to be at a low voltage and is decoupled by C23, so it shouldn't matter which.
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Old 27th Nov 2020, 7:35 pm   #3
Ian - G4JQT
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Default Re: Ekco A22 V2 suppressor grid

Quote:
Originally Posted by AC/HL View Post
That's the suppressor grid, there to remove the tetrode kink. It just needs to be at a low voltage and is decoupled by C23, so it shouldn't matter which.
Sorry, yes, suppressor grid - slip of the fingers. Normally earthed, but just curious as to why the change from circuit to construction.
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