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Old 27th December 2012, 09:14 PM   #351
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Gents,

I am now on the road, so can't work on the adapter... Another bit of info: I also ran tests on some EL84s, which has the g3 internally connected to the cathode, all the other test conditions were the same, and I had no issue with the curves - they were exactly how they should be based on the datasheet.

So I am puzzled as to why grounding the g3 externally to the cathode would be an issue with the 6P15P. Not floating the screen supply can distort the reading but not the shape of the curves, right?

Thanks,
Jaz
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Old 1st January 2013, 04:47 PM   #352
mogliaa is offline mogliaa  United Kingdom
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Hey Jaz,
First of all: happy New Year! Hope you had a good time.
Here is the 6P15P pentode trace with 150V screen bias. G3 is connected to cathode and screen supply is floating with return to the cathode (I have my sensing resistor in the cathode).

6P15P Pentode | Bartola Valves
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Old 1st January 2013, 08:41 PM   #353
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Quote:
Originally Posted by mogliaa View Post
Hey Jaz,
First of all: happy New Year! Hope you had a good time.
Here is the 6P15P pentode trace with 150V screen bias. G3 is connected to cathode and screen supply is floating with return to the cathode (I have my sensing resistor in the cathode).

6P15P Pentode | Bartola Valves
Ale,

Happy New Year!

As usual, great looking curves! Will try and find out what's wrong with my setup or tubes (they are Chinese, not even the Russian ones...)

Cheers
Jaz
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Old 1st January 2013, 08:53 PM   #354
mogliaa is offline mogliaa  United Kingdom
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Jaz,
Can you post an example of a pentode trace that works for you and how are you connecting each element and power supplies?
Thanks
Ale
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Old 2nd January 2013, 12:33 AM   #355
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Quote:
Originally Posted by mogliaa View Post
Jaz,
Can you post an example of a pentode trace that works for you and how are you connecting each element and power supplies?
Thanks
Ale
Here is the test setup and result for the 6P14:
Click the image to open in full size.

I think I also isolated the cause of the problem with the 6P15 - it seems that the screen grid is drawing a lot of current so the supply goes into current limiting, and there is also parasitic oscillation present - this is the first tube that I am having problem with, will investigate further...

Thanks,
Jaz
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