Thread: AVO VCM Mk 3.
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Old 7th May 2020, 7:49 pm   #2
Dekatron
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Join Date: May 2009
Location: Linkoping, Sweden
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Default Re: AVO VCM Mk 3.

If you use 10053 Ohm across the meter it will be within 0.5% of what it should be. Otherwise I'd leave it as it is.

I've never seen RV3 & RV5 exchanged in any schematic, RV5 being the Grid Volts potentiometer and RV3 being the mA/V potentiometer in all that I have.

There is one error that can be found in many of the schematics for the AVO Mk III and that is that R39 @ 750 Ohm is missing. It is positioned between R32 and the switch contact in the mA/V position on the Meter Switch so that R32 is shorted by the "inner" position on the slope switch but R39 is always connected. See the cutout from my corrected schematic. There might be Mk IIIs out there that is missing this resistor but all that I have repaired have had this resistor.

AVO had a lot of errors in their schematic diagrams and seems to have forgotten to add modifications in them when they changed details in their VCMs.
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