Picture Tube Tester

[jshorva65]

First, the gun selector should be in position "R" as this is the "B/W" position on all testers I've ever seen. If you're testing a color tube, though, there is a gun connected regardless of the position of the switch, but for B/W tubes there is nothing to test unless the gun selector is set to the position to which the gun's elements are actually connected (almost always the "R" position).