Avo valve

Well what I inderstand is when you power on the Avo 2 panel 1. This indicator lamp should light to show the unit is on 2. When testing a valve for shorts, it should light up to show if there isnt a short. So when I turn the unit on it does not light up, then when I check a tube which Im using in a amplifier and know is working it again does not light up.
 
Traditionally the short lamp lights when there is a short. Normally off and almost infinate life. The neon light is used since it uses very little current to light. If you have a tube with a short or know which pins on the socket to short you could test the ;lamp.