Testing Parameters from Tube Manufacturers

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Testing Parameters from Tube Manufacturers

Postby Allan » Fri Jul 19, 2013 3:27 pm

Hello everyone.

This question may relate closer to manufacturers' data sheets more than tube testers. Here goes. Can anyone tell me what an EL34 or 6CA7 will draw for plate current at the following configurations and voltages?

Triode configuration: 450 Volts at the anode (Va), and -40 Volts bias (Vg1)

Triode configuration: 465 Volts at the anode (Va), and -41 Volts bias (Vg1)

Pentode configuration: 450 Volts at the anode (Va), 450 Volts at the screen grid (Vg2), and -40 Volts bias (Vg1)

Pentode configuration: 465 Volts at the anode (Va), 465 Volts at the screen grid (Vg2), and -41 Volts bias (Vg1)

Shuguang's Treasure Series of 6CA7 have been seen tested at the above voltages. This is according to the test paper that each of these tubes comes with. However, this test paper does not specify if the testing is in triode mode or pentode mode. I have seen these tubes being sold with plate current readings of as low as 33mA to as high as 60mA. It would be much easier to test these with the old Mullard pentode spec of 250V plate, 250V screen grid and -13.5V bias. I wish Shuguang would do this. Then I could just order a pair of 100mA and know that it compares to my other EL34s.

I have looked through the old Philps/Mullard/Telefunken/Sylvania data sheets but cannot find voltages as above. I appreciate any help.
Thank you.

-Allan
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Allan
 
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Re: Testing Parameters from Tube Manufacturers

Postby Doc10 » Sun Jul 28, 2013 8:05 pm

Hello,

here is the datasheet of 6CA7. Note 6CA4 this is a beam tetrode, that is
"supposed" to be equivalent to EL34 which is a pentode.
So you should better refer to a 6CA7 datasheet and not EL34, to verify your tubes.

http://4tubes.com/DATASHEETS/SCANS-Orig ... NG-SOL.pdf

Such tubes are often tested on fixed voltages, and then simply measuere the
current with each one. Like that you can test 50pcs all together quickly.
To avoid overload they use 250V plate and screen. That is still pentode,
but grid volatge is the same as triode mode because plate and screen are
the same voltage. Only Rp and gain is another in triode mode. In Triode
mode, the screen current is added to the plate current.

Take the Tung Sol datasheet to see if your tubes are conform. If not,
they are not. Anyway, there is no objection to re-test them at
any other point you like, such as the Mullard.
Also in that case, they must be the same as the Tung-Sol datasheet.
Doc10
 
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