Thread: Valve Testing
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Old 19th Oct 2012, 5:39 pm   #6
radiozero
Hexode
 
Join Date: Mar 2008
Location: Wakefield, West Yorkshire, UK.
Posts: 438
Default Re: Valve Testing

I might be on the trail:

When you put certain voltages onto the grids, (as per AVO Valve Data ) an expected anode current will flow. That current is shown on AVO Valve Data (under heading "Data For Valve Characteristic Meter and Valve Tester Type 160") as 65mA. (No anode current figure given under heading "Data For AVO Valve Tester" - curiously! No idea why!).

So, I suppose that if cathode emission is good you will see 65mA on the scale. Anything less than 65mA tells you that you have something of a cathode emission problem. Here, you are not using the "goodness" scales on the meter. Just noting the actual anode current. However, the anode current is an initial indication of "goodness".

But, we have not measured mA/V yet.

To measure actual mA/V we obtain a balance condition concerning the meter (using the Backing Off Control). That sets the meter to read 0 mA. Now, the mA/V button is pushed and the anode current changes. If you now get 7.3mV on the scale, that means change in current is 7.3mV. If what I say is correct, and the valve is healthy, then pressing the mA/V button 1V was added to whatever potential was on the grid.

So far we have not used the comparative goodness scale. I don't know how that works.

Last edited by radiozero; 19th Oct 2012 at 6:02 pm.
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