Computer Monitor Heater (filament) Voltage
Standard Computer Monitor heater voltage is 6.3 volt dc but some designs run up to 7 volts dc ! In some older Monitor designs like the VGA that only support until the 640 by 480 resolution, the heater voltage may derived from the flyback transformer winding like the Television. The voltage output from the flyback transformer is high pulse ac thus it can’t be measure by a normal ac volt meter. To check the presence of the heater voltage, one just have to view the neck of the CRT tube for any glow. Now all of the CRT Monitors in the market are using DC voltage derived from the power supply. To measure it just use a normal voltmeter (analog or digital) and set it to DC range. Don’t be surprise that I do came across Monitors that used negative 6.3 volt dc. A heater is just like a light bulb, it can work in ac, +dc or even -dc! By the way, the heater is very durable, so an open filament is not a very common problem. If it opened, there is no way we can repaired it.