Power up the amplifier, and watch for any deflection on the meter.If you cannot see much of a meter reading, go downward through the voltage scales (usually this would be 50, 15, 5, and 1.5).
Accordingly, the ohms-per-volt sensitivity changes with the range selected.
Just as the name implies, VTVM is the acronym for Vacuum Tube Volt Meter.
Therefore, as expected, there are honest-to-God vacuum tubes inside your VTVM.
Next, use your isolation probe, and set your VTVM DC voltage scale to ‘150’.
Connect the isolation probe to the ‘open’ end of the coupling capacitor, and the ground clip to the chassis.