03-11-2022, 05:53 PM
It's a bridge with the magic eye replacing a meter. The eye changes how much it's open near balance. I forget if actually balanced is the eye as open or as closed as it goes, but you'll easily see which it is.
It's likely from the 1950s.
It will need some of the internal paper dielectric capacitors replaced.
The neon is usually part of a relaxation oscillator. It doesn't light when the terminals are open and will appear on with a low resistance or short. My stand alone neon leakage tester uses about 500V via 2 x 1 M Ohm in series for safety. It will flash quickly with 10 M Ohm and slowly with 100 M Ohm.
A leaky paper cap (or any electrolytic or a too low volatge rated cap) will likely make the neon light. It may flash slow or fast according to leakage, assuming there is internally a 100nF (0.1uF) very low leakage cap across the neon. A polyester or polycarbonate type. Original cap, if fitted, will be too leaky.
The paper dielectric caps had about 10 year life. Some are in waxed card tubes, some in aluminium or steel cans and some in now crumbling plastic. Only the hermetically sealed ones last (Military PIO with hermetic seals, not rubber bungs).
It's likely from the 1950s.
It will need some of the internal paper dielectric capacitors replaced.
The neon is usually part of a relaxation oscillator. It doesn't light when the terminals are open and will appear on with a low resistance or short. My stand alone neon leakage tester uses about 500V via 2 x 1 M Ohm in series for safety. It will flash quickly with 10 M Ohm and slowly with 100 M Ohm.
A leaky paper cap (or any electrolytic or a too low volatge rated cap) will likely make the neon light. It may flash slow or fast according to leakage, assuming there is internally a 100nF (0.1uF) very low leakage cap across the neon. A polyester or polycarbonate type. Original cap, if fitted, will be too leaky.
The paper dielectric caps had about 10 year life. Some are in waxed card tubes, some in aluminium or steel cans and some in now crumbling plastic. Only the hermetically sealed ones last (Military PIO with hermetic seals, not rubber bungs).
