Troubleshooting DELL E173FPB LCD Monitor with power blink symptom is quite easy if you know the right procedure to test it. There are two sections in the monitor that can cause power to blink. It is either primary or secondary section or even sometimes both sections can be faulty. So to isolate as which section is giving problem. I used an automobile 12 volt light bulb (brake light) and connect it between the 12 volt supply line and cold ground with the fuse removed. If the bulb still blink chances is very high the power primary section have problem.
Do not overlook the other voltages line as well such as the 3.3 and 5 volts. If any components shorted that gets the supply from the 5 and 3.3 volts, the power also may blink. If the 12 volts bulb lights up we can assume 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 continue to check the power section, it will be going to waste your time. You should now concentrate on the secondary section circuit such as the four transistors C5707 that drive the high voltage transformer in the inverter board.
Just think these transistors like horizontal output transistor (HOT) in the CRT monitor 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 have a shorted reading with an ohmmeter.. This transistor can get faulty by itself or it could be some others components that caused it to develop a short circuit such as a defective high voltage transformer but all of the four high voltage transformers checked to be okay with ringer and ohmmeter test.
Now, here is the secret that I’m going to reveal. If you just replace the defective transistor 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 analog or digital meter. If you use both meters to test the transistors then you have missed out on the faulty transistor because both meters won’t reveal to you the hfe reading of the transistors. Only some digital meters have the hfe checking feature. In other words, you have to use test the hfe reading of a transistor. Although you can replace the other three transistors directly, why not we do some detective work to find the cause of the problem?
Using the Peak electronic atlas component analyzer, I could clearly see the different between a good and a bad transistor. A good C5707 transistor has hfe reading from 320 to about 390 but the bad one reads 467! The other two C5707 transistors have reading about 350. In the above case only two C5707 transistors were replaced and you save the other two. I had burn in test this LCD monitor for many days and it worked perfectly fine.
Conclusion- Whether you repair the DELL E173FPB LCD Monitor 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 Monitor too.
