[Milsurplus] 71A tube

[Ray Fantini]

I am in the process of restoring a Weston OQ-2 tube tester. The question I have is why did they use a 71A tube, a triode as a rectifier for obtaining DC voltage for the short test? What advantage is their to using a triode with the grid connected to the plate as a diode? Not to mention that the plate current capability of that tube is only about 10 Ma. So why did they do this? Was thinking of replacing the defective tube with a diode and a current limiting resistor installed in an old tube socket but wanted to know why they did this in the first place.
Ray Fantini KA3EKH