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Old 28th April 2012, 05:10 PM   #1
diyAudio Member
 
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Default Problem with ECC83 measurement values - please help

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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Old 28th April 2012, 08:43 PM   #2
diyAudio Member
 
Join Date: Feb 2011
Location: South Wales, UK
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.
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Old 29th April 2012, 10:29 AM   #3
diyAudio Member
 
Join Date: Apr 2012
Quote:
Originally Posted by payitforwardeddie View Post
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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Old 29th April 2012, 02:19 PM   #4
diyAudio Member
 
Join Date: Feb 2011
Location: South Wales, UK
I'm wondering if this is a genuine ECC83 or a chinese clone. The Ia doesn't seem right but whether it affects performance will depend on the circuit its used in.
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Old 29th April 2012, 07:31 PM   #5
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ok eddie, i have to ask him - probably a guitar pre-amp methinks - also, how does he get/measure? this partial loss of vacuum and one-half has the leak between grid/cathode?

thanks for again so much for your helpful replies - susan
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Old 29th April 2012, 07:37 PM   #6
DF96 is offline DF96  England
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The picture shows a Philips-style glass seam, so unlikely to be a Chinese clone. Not necessarily made in a Philips factory, though, as their equipment was installed in other factories in the latter days of valves.
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