In lg tv repair merstham, if no display you is just not be able to know if the inverter panel is working or not unless you how to use oscilloscope to point close to the inverter board and the range could display a waveform indicating the inverter panel is functioning.
A flawed main board could cause no display problem in LCD Monitor. If there is a problem in the key board, it would not send a “on” (enable) signal to the soft start circuit and no voltage will flow to the inverter IC thus no waveform produce by the high voltage transformer.
Inside the above case, after the cover was removed, the essential thing I check was your vcc (supply voltage) to the inverter IC. It is using the famous TL1451ACN Pulse width modulation (PWM) IC-some preferred to call it as inverter IC. Pin 9 is the VCC supply input and it should have about 12 Volts when the power is “on”. Measuring the pin with my dedicated digital multimeter, it reads only about 3 volts which indicates there’s a problem in the supply collection. It could be components that are faulty that dragged down the road or it could be the swap mode power supply itself that don’t produce enough power.
In order to find the answer as which section is offering problem, the first clue was that the ability BROUGHT indicator lit and this demonstrate that the IC is supplying enough power to the circuit. Another hint is that the meter is registering about 16 volts at the input of the 2A fuse. Since of these clear solutions, we can conclude that the switch mode power supply is working fine. You can also use a 12 volt light bulb to confirm it. You may read my other post on FLATSCREEN Monitor repair articles which discusses using 12 watt light bulb for troubleshooting purposes.
I kept on asking myself, why the voltage drop to three volts after the fuse. Ahead of the blend it reads about 16 volt but after the blend it reads only 3 volts! I didn’t think the fuse, because the fuse can only either yes or no and no among. The first circuit that I examined was the start signal but all components checked to be okay. I actually even desoldered the pin number 9 of TL1451ACN inverter IC just to make certain it is not this IC that pulled throughout the volt quality.
This problem really challenges my troubleshooting and fixing skill, because almost all suspected components already examined to be working. Even the start circuit diffusion (C945 & A733) We direct replaced, afraid they would breakdown when under load. The only element that I didn’t check was your fuse! By using my meter put across the fuse, rather than getting low ohms or no ohm reading I acquired one. 012 Kilo ohms! I have got a surprised and don’t believe a fuse can actually go into high ohms rather than open up circuit. I usually thought that a fuse will either be close up or open circuit. The fuse with zero ohms turned into high ohm thus the 16 v dropped to 3 v! I’ve came across a lot of this type of blend but this is the very first time a fuse transformed into high resistance.