The complaint for this DELL E152Fpb LCD was when switched “ON” has power (LED lit) but no display. LCD is different from the CRT where you could feel the static at the front of the picture tube or hear the rushing sound from the high voltage produced by the flyback transformer.
In LCD, if no show you won’t be able to grasp if the electrical converter board is functioning or not unless you employ associate CRO to purpose close to the electrical converter board and therefore the scope may show a wave shape indicating the electrical converter board is functioning.
A faulty Main board could cause no show downside in digital display. If there is a problem in the Main board, it would not send an “On” (enable) signal to the soft start circuit and no voltage will flow to the supply pin of inverter IC thus no waveform produced by the output of high voltage transformer.
In the higher than case, after the cover was removed, the first thing I check was the VCC (supply voltage) to the inverter IC. This model is mistreatment the far-famed TL1451ACN Pulse breadth modulation (PWM) IC-some most well-liked to decision it as electrical converter IC.
Pin 9 is the VCC supply input and it should have about 12 to 14 Volts when the power is “On”. Measuring the pin with my devoted digital multimeter, it reads only about 3 volts which indicates there’s a problem in the supply line. It may be elements that ar faulty that dragged down the road or it may be the switch mode power offer itself that don’t manufacture enough power.
In order to seek out the solution as that section is giving downside, the primary clue was that the ability LED indicator lit and this prove that the IC is activity enough power to the circuit. Another clue was that the meter is registering about 16 volts at the input of the 2A Pico fuse.
Because of these clear answers, bush tv repair london can conclude that the switch mode power supply is working fine. You can also use a 24 volt light bulb to confirm it. You may have already read my other LCD repair article which talks about using 24 volt light bulb for troubleshooting purposes. I unbroken on asking myself, why the voltage drop to 3 volts after the fuse.
Before the fuse it reads regarding sixteen V however once the fuse it reads solely three volts! The first circuit that I checked was the beginning circuit however all elements checked to be okay. I even desoldered the pin nine of TL1451ACN electrical converter IC simply to create positive it’s not this IC that force down the voltage.
This downside very challenges my troubleshooting and repairing ability, because almost all suspected components already checked to be working. Even the beginning circuit transistors (C945 & A733) I direct replaced, afraid they would breakdown when under load. The only element that I didn’t check was the fuse!
By mistreatment my meter placed across the fuse, instead of getting low ohms or zero ohm reading I got 1.012 Kilo ohms! I‘ve got a shocked and don’t believe that a fuse will really get in high ohms rather than electrical circuit. I forever thought that a fuse is either shut or electrical circuit.
A fuse with low or zero ohms become high ohm so the sixteen volts born to three volts! I’ve came across lots of this type of Pico fuse but this is the first time a fuse changed into high resistance. Replacing only the fuse put the DELL E152Fpb LCD back to life.
The lesson learned from here is that don’t assume that a element is usually in an exceedingly sensible operating condition. You have to verify it along with your meter and if you continue to suspect the element is giving downside, merely replace it with a familiar sensible one and retest the instrumentality. For your information, electronic components can breakdown when under full operating voltage.«Read More