Growing family of my Hallicrafters devices requires some maintenance and restoration work. The heart of every receiver or transmitter are the vacuum tubes. They are very old and usually in unknown state. Checking them is possible either by checking that radio works at all or measuring their parameters with some special devices.
This is where tube tester comes to the stage. It applies the filament power to make the cathode hot and voltages to the plate and grids. With specified values of these voltages the specific current should flow through the tube. If is according to specification then most probably tube is okay, otherwise needs to be replaced.
For the filament power I used ready module of the power supply. It allows to set the voltage and current limit so specific values so it is possible to "wake up" old tubes with lower filament power at the begining. According to one of my friends the filament heater can be sometimes damaged if is not used for several years and the full voltage is applied.
For the plate and grids I used ready tube tester module that I got from eBay. It allows to set plate voltage up to 500V, set Grid 1 & 2 voltage and measure the plate current. The measurement is done in short impulses only what prevents damage of the tube in case od wrong wiring or incorretly set parameters.
I have tested some tubes residing in the shelf. The values were exactly as expected from the specification.
