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Problem with ECC83 measurement values - please help

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Hi,

I have given some ECC83's to a friend who has measured one of them and says - "and found that this tube is not suitable for use, due to deformation of the electrodes and partial loss of vacuum (it has a current value greater than 2 - 3 times against the passport, and one-half has the leak between grid/cathode)"

He seems to think I got the Ia and gm values mixed up - this valve was measured by someone I know with a tester and he wrote the values on a label on the valve (see picture) - it looks like the Ia's are at 2.8 / 2.5; I take it the Sa? is the gm value?

So the gm's look within spec for this valve but the Ia is too high (should be 1.2mA)? Is this a bad thing?



And how does he know there's a "partial loss of vacuum" and what this "one-half has the leak between grid/cathode" mean please?

Any help would be greatfully appreciated - thanks

Susan
 

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You gave your friend a number of these. Must be a good friend. Have you seen the price of these on Ebay.
Anyway, check out this very good site for info
http://www.r-type.org/pdfs/ecc83.pdf

I imagine the ECC83 in question has been tested correctly?
The Ia values will depend upon the grid/cathode volts and the anode volts which may be totally different to in circuit values.
If you look at the datasheet above, you'll see that Gm is listed as "S".
Hope this helps.
 
You gave your friend a number of these. Must be a good friend. Have you seen the price of these on Ebay.
Anyway, check out this very good site for info
http://www.r-type.org/pdfs/ecc83.pdf

I imagine the ECC83 in question has been tested correctly?
The Ia values will depend upon the grid/cathode volts and the anode volts which may be totally different to in circuit values.
If you look at the datasheet above, you'll see that Gm is listed as "S".
Hope this helps.

Hi Eddie - thanks for the reply - I believe he used this data sheet to test, so Va @ 250V, Vg @ -2.0V giving Ia's of 2.8mA/2.5mA.

So I'm asking, at these values, is a substantionally stronger Ia a bad thing?

Thanks
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.