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radiozero · 21st Oct 2012, 1:03 pm

Let me just recap what I think I now know:

Manufacturers produced a set of static DC operating conditions for valves, for instance, the KT66. There were various conditions for this valve: As Beam Pentode, as Triode, and class A or AB1, single valve or double valve. These are genuine typical static DC operating conditions to guide the designer.

These manufacturers conditions are included in your general Valve Data books.

These conditions can be used in valve testing. But, they do not strictly have to be adhered to. Because you can alter the DC volts conditions and produce an appropriate value of anode current and mutual conductance associated with a new and healthy valve, which will of course differ from the published operating conditions. Many valve tester manufacturers have taken that approach, depending on the model. Then we obtain a set of tables specifically for valve testing, on a specific valve tester model.

This is what we see when we look at AVO valve testing data. We are looking at model-specific valve testing data, which may or may not agree with a valve's operating conditions. In fact, for the KT66 (not sure about other valves), neither the Type 160 or MKI or MKII testers manage to test this valve at it's manufacturer's operating conditions.

Now, we have the question of what can the MKI and MKII measure. Clearly the MKI and MKII can measure anode current. And, when you do, you can try to infer something about the valve. But, there is no anode current given under the heading "DATA FOR AVO VALVE TESTER". Current value is only given for the Type 160. So, what is the point of noting the anode current, when you have no figure to go by for the MKI and MKII? You are only given Gm.

I bought my AVO MKI hoping to test my KT88s. I hope there is a work-around. When I concocted a homebrew test circuit for current, I got oscillation. I killed it with ferrite beads. So, it readily oscillates. But, even if I kill oscillation, I have no test data for the MKI - "No Data Available" for the MKI and MKII. Apparantly.

21st Oct 2012, 1:03 pm	#14
radiozero Hexode Join Date: Mar 2008 Location: Wakefield, West Yorkshire, UK. Posts: 444	Re: Valve Testing Let me just recap what I think I now know: Manufacturers produced a set of static DC operating conditions for valves, for instance, the KT66. There were various conditions for this valve: As Beam Pentode, as Triode, and class A or AB1, single valve or double valve. These are genuine typical static DC operating conditions to guide the designer. These manufacturers conditions are included in your general Valve Data books. These conditions can be used in valve testing. But, they do not strictly have to be adhered to. Because you can alter the DC volts conditions and produce an appropriate value of anode current and mutual conductance associated with a new and healthy valve, which will of course differ from the published operating conditions. Many valve tester manufacturers have taken that approach, depending on the model. Then we obtain a set of tables specifically for valve testing, on a specific valve tester model. This is what we see when we look at AVO valve testing data. We are looking at model-specific valve testing data, which may or may not agree with a valve's operating conditions. In fact, for the KT66 (not sure about other valves), neither the Type 160 or MKI or MKII testers manage to test this valve at it's manufacturer's operating conditions. Now, we have the question of what can the MKI and MKII measure. Clearly the MKI and MKII can measure anode current. And, when you do, you can try to infer something about the valve. But, there is no anode current given under the heading "DATA FOR AVO VALVE TESTER". Current value is only given for the Type 160. So, what is the point of noting the anode current, when you have no figure to go by for the MKI and MKII? You are only given Gm. I bought my AVO MKI hoping to test my KT88s. I hope there is a work-around. When I concocted a homebrew test circuit for current, I got oscillation. I killed it with ferrite beads. So, it readily oscillates. But, even if I kill oscillation, I have no test data for the MKI - "No Data Available" for the MKI and MKII. Apparantly.