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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 1st Feb 2023, 4:54 pm   #1
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,755
Default AVO test results

I have broken out the grid and anode connections from my Mullard Tester so I can take accurate anode current readings and do static gm tests (it's very easy as the connections can be taken from the push switches).

In the past I have been using the 'AVO Valve Data Manual' as a guide to what a valve should do but I am now not so sure this is valid.

I tested an EL37 using test card 262 that has Va=250, Vsg=250, Vcg=-13.5 (77 is the official card but 262 is the AVO test conditions) and it measures 87mA. The AVO data says 100mA and that appears to roughly match the datasheet.

I then tested a KT66 using test card 262 again and the anode current measures 95mA. The AVO data sheet implies it should be 65+10 (adjusting for -15V) or about 75mA. Then if I go to the datasheet 95mA looks about right.

My measured currents may be a little low as I don't wait till they fully settle (anode dissipation exceeds specs) but my assumption that the AVO data corresponds to manufacturers DC specification is clearly wrong and why test a KT66 at 65mA and an EL37 at 100mA?
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