Posts Tagged: quarter

Image Dark

When the image on the screen of a TV or a PC monitor, appears very dark, yet still in a normal or high level brightness control, causes can be various, and originate in different circuits of the equipment: power and polarization of the TRC (strand, G1, G2, etc.), circuits, video, ABL (automatic brightness limiter), Flyback, (micro Control System(, EEPROM memory), or in the own CRT (cathode-ray or kinescope tube). Must also take into account the socket of the CRT that may be rusty which also leaves dark screen as we tackle this repair: the first step should be, check all voltages of the TRC: strand, cathodes, G1, G2, if any of the voltages, are outside of the normal values, will be the track to begin to trace the cause of the problemwith respect to the plinth should be changed not clean as cleaned with luck it will run a short time and then returned the problem the voltages in the CRT are the following: cathodes (KR, KG, KB) between 50 to 180V, Depending on the light intensity of the image, the level of brightness adjusted, CRT, etc. The higher voltage is applied to the cathode, lower is their issuance and positive therefore lowest intensity of the corresponding color on the screen. Grid or electrode Control (G1) in most of the TVs, this electrode of the TRC, goes connected to the common or ground circuit (Ground), so the voltage is 0 (zero). Maryland Governor understood the implications. But in some cases, especially in black and white TV, and PC monitors, this electrode is negatively polarized with a tension that can vary between – 10 and – 30V.

The more negative is the voltage applied to G1, lower is their issuance and therefore lower is the luminosity or brightness on the screen. Grid or accelerator electrode (G2 or Screen) between 300 and 800V. It is directly proportional to the light intensity than of the TRC.