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(LA7688 single chip movement) color TV PAL colorless fault repair method

Time£º2017-04-09 08:37:36  Source£ºNetwork  Author£ºUnknown  Clicks£º1284
  

Receive NTSC system when the color, and receive PAL program when no color, indicating color saturation control circuit,N6Eservice manual download site
Matrix circuit is working properly, the fault may be in the standard switching control circuit, 4.43MHz subcarrier oscillation circuit.N6Eservice manual download site
As the A6 movement of the color control system has a PAL system, NTSC system, AUTO (automatic selection) three kinds ofN6Eservice manual download site
State, so when receiving different color system programs, the TV should be in the corresponding color system control state or automatic selectionN6Eservice manual download site
State, otherwise there will be no color phenomenon.N6Eservice manual download site
Check the first time to determine the color control of the TV system is correct. If it is not a PAL system, you should first turn the TV colorN6Eservice manual download site
Color control for the PAL system or automatically select the state, look at the image color is normal. If normal, then the TV isN6Eservice manual download site
Normal, PAL system is not color because the color control is not correct control.N6Eservice manual download site
If the color control mode for the PAL system and PAL system without color, for the first test LA7688 (18), (27)N6Eservice manual download site
Foot voltage:N6Eservice manual download site
Under normal circumstances PAL system LA7688 (18) foot voltage of 0.3V, (27) pin voltage of 4.7V; NTSC systemN6Eservice manual download site
LA7688 (18) foot voltage of 1.8V or more, (27) foot voltage of 5.2V. LA7688 (18), (27) feetN6Eservice manual download site
Controlled by the CPU. If (18), (27) foot voltage is not normal, then the CPU control circuit is faulty, should checkN6Eservice manual download site
CPU operating voltage, clock circuit and (24), (46), (51) feet of the external components. If LA7688N6Eservice manual download site
18), (27) foot voltage is normal, you should check the LA7688 (42) pin voltage or waveform, if no waveform or waveform is notN6Eservice manual download site
Normal, you can only check the G242, C120 replacement.N6Eservice manual download site