I have a Heathkit Model V-5 Vacuum Tube Voltmeter (VTVM). This instrument was sold by Heathkit in the early 1950's. The VTVM measures dc and ac volts and ohms. It has a very high input impedance. The circuit incorporates two vacuum tubes - a 6H6 and a 12AU7.
When I received the meter, it worked fine, but the meter needle rubbed on the metal metal scale. I removed the meter clear cover, carefully removed the scale and carefully bent the metal scale to where it was flat. After reassembly, the meter work as it should.
