How To Repair DELL E151FP LCD Monitor With No Power Symptom

The DELL E151FP LCD Monitor came in with no power symptom and upon opening up the cover I saw few components that were burnt. R623 (4.7 ohm) burnt at the side and you could still recognized the resistor color code. The current sense resistor (0.68 ohm) outer layer partly had came off and slightly burnt and the filter capacitor c605 (68uf 400v) one of the pins had became rusted and came off when I tried to desolder the pin.

This is not a new model and I believe lots of experienced techs had solved the problem. But for those who haven’t come across this problem, you may use the procedure to troubleshoot and repair any other type of LCD Monitor with power problem.

I will first remove the power transformer and make sure it rings okay with dick smith flyback tester. I do this first because I don’t want to waste my time checking other components and later only found out that the power transformer is the caused of the power problem.

Once it rings okay I will measure all the secondary diode. For your information most LCD Monitor power supply widely used the dual schottky type diodes and the specification usually in the 10 to 20 amp with about 40 volts. However I do come across some designed are still uses the ultra fast recovery type diodes in the secondary section.

Make sure you know how to check a normal diode and a schottky diode. Refer back to my website in the diode section and search for testing schottky diode article. I will then check for the ESR of electrolytic capacitors too.

Once I confirmed that the secondary side components are all tested okay, I would then proceed to remove all the components in the primary side. Some components in the primary side you can check on board like the bridge rectifier and fuse. If I’m new to the LCD Monitor model I would check all components off board (with a lead removed from board). With this way you will be sure that all components you have scanned through.

These are the components that I found defective; fuse-2A, R615-0.68 ohm, R613- 1K, R612-47 ohm, R623-4.7ohm, D604-1N4148, Q601-SSS6N60A, C605-68UF 400V and IC601-UC3842B. Total was nine components and it took me less than 20 minutes to check all the components in primary side. Now is the time to search for spare parts. After spending about 5 minutes in the spare part compartment I managed to find all components except the power fet SSS6N60A.

Though this part number is mostly used in switch mode power supply, my electronic supplier does not have this in stock. I would then browse through the semiconductor databook to search for equivalent part number. From the book, it suggests to use the K1118 as replacement. After all components have put into their original place or location and of course with the power transformer soldered, I don’t immediately switch on the power supply.

I would first use a 100watt light bulb connected in series with the live line. The best place to put the light bulb is the fuse holder area. Remove one of the fuse lead and connect the light bulb across it. Power it on and begin to observe the bulb.

If it brightly lit and stay that way then there is still problem in the power supply. However, if the bulb doesn’t light at all then this is a good sign that the power supply may be working.

Use a multimeter to place at the secondary side with power on. If you get some accurate voltage reading from the outputs and the bulb doesn’t light at all, then this confirmed that the power supply is working. Switch off the power supply and connect back the fuse and turn the LCD Monitor on again.  I’m very sure the LCD Monitor will now work.

Whether you are troubleshooting the DELL E151FP LCD Monitor or other brands, you can always use the procedure given above to repair the power supply problem. This method can be even use to repair other types of power supply too. No matter what types of power supply you are troubleshooting, just make sure you know how to check and test the basic electronic components. If you ever miss one, sad to say you would not be able to solve the problem or it might just take you many of your precious hours to complete the job. Happy hunting!

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