Troubleshooting DELL E173FPB LCD with power blink symptom is quite easy if you know the right procedure to test it. There are two sections in the LCD that can cause power to blink. It is either primary or secondary section or maybe generally each sections may be faulty. So to isolate as that section is giving drawback.
I used an automobile 24 Volt light bulb (brake light) and connect it between the 12 volt supply line and cold ground with the Pico fuse (along the 12 Volts line) removed. If the bulb still blink probabilities is incredibly high the facility primary section have drawback. Do not overlook the opposite voltages line still like the three.3 and 5 volts.
If any parts shorted that gets the provision from the five and three.3 volts, the power also may blink. If the 24 Volts bulb lights up we can assumed that the power supply is working fine and something shorted further down the line that makes the power supply to blink. If the bulb lights and you still check the facility section, it will be going to waste your time. You should currently target the secondary section circuit like the four transistors C5707 that drive the high voltage electrical device within the electrical converter board.
Just think these transistors like the horizontal output transistor (HOT) in the CRT that drive the flyback transformer where it worked so hard and chances for it to breakdown is very high. Checking the four transistors off board found one of them has a shorted reading with an ohmmeter.
This semiconductor unit will get faulty by itself or it may be some others parts that caused it to develop a brief circuit like a defective high voltage electrical device however all of the four high voltage transformers checked to be okay with ringer and meter take a look at. Now, here is the secret that sony tv repair london going to reveal to you.
If you {only|you simply} replace the defective semiconductor unit only, chances is very high the transistor or another C5707 transistor will breakdown again. Usually what a technician does is to test the other transistors with either an analogue or digital meter. If you utilize each meters to check the semiconductor units then you’ve got disregarded on the faulty transistor as a result of each meters won’t disclose to you the hfe reading of the transistors.
In other words, you have to test the hfe reading of a transistor. Although you’ll be able to replace the opposite 3 transistors directly, why not we do some detective work to find the cause of the problem?
Using the height electronic atlas element instrument, I could clearly see the different between a good and a bad transistor. A good C5707 semiconductor unit has hfe reading from 320 to regarding 390 however the unhealthy one reads 467! The other 2 C5707 transistors have reading regarding 350. In the higher than case solely 2 C5707 transistors were replaced and you save the opposite 2.
I have burned in test this LCD for many days and it worked perfectly fine. Conclusion- Whether you repair the DELL E173FPB LCD or any other model such as the E172FPB or E171FPB, basically the testing method is the same. You could also use this testing procedure on other brand of LCD too. Please check also to see if there are any dry joints (solder) in the surrounding circuit like the legs of the high voltage transformer.