This is a Hickok 534 that I repaired and calibrated for a Customer. The Customer asked me to wire a Bias fuse bulb and test points for checking plate current.
The Hickok 534 has a built in multi-tester with VOM capability. This model has a common failure in the multi-tester circuit that switches the meter from tube testing to multi-meter testing that causes the meter to not operate when testing tubes.
The plate current test points have a precision resistor so a millivolt meter can be installed to measure the voltage across the resistor that is proportional to the current in the plate circuit. A current meter is not required to measure the plate current and a jumper is not required to test tubes when not measuring plate current.
It is a good idea to install a Bias fuse bulb in tube testers that don’t have a fuse bulb. Over current through the Bias pot can cause damage and there are no replacements available for the custom wire wound Bias pot.