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Old 13th Apr 2018, 11:06 am   #1
ms660
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Default Avo Two Panel Valve Tester Voltages

Looking at the online copy of the EMER manual for the two panel valve tester there appears to be some errors in part of the technical description, the anode/screen transformer voltages shown on the schematic and the anode/screen voltage selector switch positions ID letters in that same schematic:

https://frank.pocnet.net/instruments...s/AVO-EMER.pdf

Or have I lost the plot?

Lawrence.
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Old 13th Apr 2018, 11:57 am   #2
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Default Re: Avo Two Panel Valve Tester Voltages

David made this up a few years ago, might be of use;
Attached Files
File Type: pdf AVO 2 Panel Schematic from dave.pdf (151.8 KB, 113 views)
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Old 13th Apr 2018, 12:10 pm   #3
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Default Re: Avo Two Panel Valve Tester Voltages

I've seen that one, it's very nice, but again the voltages etc seem wrong to me?

Lawrence.
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Old 13th Apr 2018, 5:58 pm   #4
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Default Re: Avo Two Panel Valve Tester Voltages

There are some discrepancies between what is written in different schematics and on the front panel, also between how different schematics show how the switches are connected to the transformer.

The only way of knowing what is correct is to look inside your tester and trace the wiring and measure the voltages. I don't own any of these testers so I can't say how a correct wiring nor voltages should be. I believe that the circuit drawn by david was traced from his tester so it does at least look like his tester.

From the circuit diagrams, and voltages printed in the circuit diagrams that I have, I can only say that sometimes the voltage has been printed as 1.4142 times higher - 350 for the 250 on the Anode switch and so on, but there are also a lot of errors/mistakes (obfuscation?) in different circuit diagrams. The Anode setting of 80 is sometimes written as 105, 100 and sometimes also as 60! (105 is closest to 80 * 1.4142 is approximately 113 and 60 * 1.4142 is approximately 85).

Maybe this is what is confusing you?
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Old 13th Apr 2018, 6:50 pm   #5
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Default Re: Avo Two Panel Valve Tester Voltages

I noticed the errors when looking at the EMER manual, the voltages implied on the schematic didn't seem to fit the DC*1.4 implied in the patent for the AC voltages to the anode, but the voltage table in the repair section of the manual does, the patent also mentions a grid shift for mA/V test of 2 volts but the EMER manual says it's 1volt.

I don't own one of these valve testers in order to check anything and I'm unlikely to, all my stuff except for an AVO 8 and a 'scope has gone, the valve testers I actually owned were a Taylor 45A many moons ago and in more recent years a 1-177-B made by Supreme.

Lawrence.
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