Quote:
Originally Posted by stevedee
I'm very sceptical about meter loading affecting voltage measurements in typical valve circuits, especially for commonly quoted test points like supply rails, anode and cathode Voltages.
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Try measuring the voltage on the triode anode of an E(U)ABC80 or any other voltage amplifier that uses a high value anode load (somewhere around 220K). The impedance here is high and you'll find that a digital meter will read a higher voltage than a 20,000 ohm per volt AVO. HT rails are a much lower impedance and wont be affected by the meter load so they will show about the same as the published voltage.
Try it with a battery valve like a DAF96 where the anode load can be several megohms.