Illuminating meters

It is very common and it happens in every shack sooner or later: a meter gets dark unexpectedly. It is very annoying when it strikes. The good old ones lamps have a period of life. Unfortunately they can not work for ever. Usually their life is quite sorter than the equipment that the meter is embedded. No big deal you can say. Just change the bulb. It is obvious. We all do this from time to time. My friend Tasos (SV8YM) had an other idea instead: To use a bright LED in the place of a bulb. LEDs can give a cold light for many years without any sign of fatigue. But there is a small problem. Their light is focused because of the lens they have. You have to sand the led to eliminate this effect. You must destroy completely the lens and leave the LED with a rough surface in order to defuse more light. You must also add a resistor of 470 Ohm in order to reduce the voltage from 13.8V to what the LED usually  needs that is quite lower. The result is perfect and you have not to worry any more about it. Take a look. The upper meter is illuminated by a bulb and the lower by the LED!