Fault finding in an LCD television receiver
Fault-finding procedure for LCD receivers follows closely that described for plasma panels.
Figure 16.33 shows the components parts of an LCD TV receiver. The start-up sequence is the same as that for plasma screens except for the absence of the resonant converter supplying the sustain voltage.
For LCD panels, a similar fault diagnosis procedure may be followed:
● Is the set in Standby?,
● Check DC outputs,
● Check voltage from Flyback switch,
● Check backlight drive voltage by placing a CRO probe in the proximity of the CCF tube step-up transformer. A sine wave signal should be picked with a frequency in the region of 50 kHz,
● Check the PWM tube brightness control pulse using a CRO or a logic probe,
● Check the inverter oscillator DC supply,
● Check inverter oscillator output.
PFC is not shown, although many large screens would incorporate it in their power distribution network.