The particular complaint for this DELL E152Fpb lg tv repair merstham was when switched on has power (LED lit) but no display. LCD Keep an eye on differs from the CRT Monitor where you could feel the static at the front end of the picture tubing or hear the rushing sound from the high voltage produced by the flyback transformer. In LCD, if no display you will not be able to know if the inverter panel is working or not unless you how to use oscilloscope to point near to the inverter board and the scope could display a waveform indicating the inverter table is functioning.
A faulty main board might cause no display problem in FLAT SCREEN Monitor. If there is a problem in the key board, it would not send a “on” (enable) signal to the gentle start circuit and no voltage will flow to the inverter IC thus no waveform produce by the high voltage transformer.
In the above case, after the cover was removed, the essential thing I check was the 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 strength is “on”. Measuring the pin with my dedicated digital multimeter, it says only about 3 v signifies there’s a problem in the supply range. It could be components that are faulty that dragged down the road or it could be the change mode power supply itself that don’t produce enough power.
In order to find the answer as which section is giving problem, the first hint was that the power LED indicator lit and also this prove that the IC is supplying enough power to the circuit. Another clue was that the meter is registering about 16 v at the input of the 2A fuse. Because of these clear solutions, we can conclude that the switch mode energy 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 lamp for troubleshooting purposes.
I kept on inquiring myself, why the volt quality drop to 3 volts after the fuse. Before the blend it reads about sixteen 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 in between. The first circuit that I checked out was the start routine but all components examined to be okay. I even desoldered the pin number 9 of TL1451ACN inverter IC just to ensure it is not this IC that pulled over the voltage.
This problem really difficulties my troubleshooting and restoring skill, because almost all suspected components already checked out to be working. Even the start circuit transistors (C945 & A733) We direct replaced, afraid they would breakdown when under load. The only component that I didn’t check was the fuse! By using my meter positioned across the fuse, rather than getting low ohms or no ohm reading I acquired just one. 012 Kilo ohms! I’ve got a surprised and don’t believe a merge can actually go into high ohms rather than open circuit. I thought that a fuse will either be near or open circuit. A new fuse with zero ohms turned into high ohm thus the 16 volts dropped to 3 volts! I’ve came across a lot of this form of merge but this is the first-time a fuse changed into high resistance.