This Dell 17 "Monitor (Made in Malaysia under LIKOM L705XXX model, product number: L7055LP) came with no power symptom. In general, after opening the lid I was on the power supply (primary side) for all burned and crack components first glance. When it is dark territory, and burnt parts are, I would say that this monitor wants a little more time, they must be repaired. If it does not (component intact) I usually start to discharge the filter capacitor and You start checking theBackup.
Okay, it is confirmed that all components of the primary in this monitor looks good.
First, the discharge of large grease filter capacitor with a resistor (I know that the tension has already drained off, but it is a normal procedure for me, because what if the start-up resistor has an open circuit?), Then You should back up.
If the backup is in order, you will learn to say that the bridge diodes work fine too. Put your black probe of your analog meter to x1 to the center Pin Set(drain) of the power FET and red probe to pin the other one) at a time (gate and source. When the pointer of the meter is not kick it 80% of the power FET okay. If you want to confirm 100% if it is good, then you need to test it out and solder. When the pointer shows a reading then most likely the power FET has developed a short circuit. The result, which I of this monitor, the pointer was not Flick.
Now is the time for me, which may Dicksmith flyback tester to select the check box isSMPS primary winding. The result I got was to have the LED panel is not illuminated. Aha! This is an indication, and the track you have been saying that they shorted either the primary or SMPS, one of the secondary diodes has made the place. Of course, you can check all the secondary diodes using your normal multimeter first (remember, every electronic shops have their own methods and processes used for troubleshooting), but I prefer this way, I also confirm when the wish SMPS primary winding, is working ornot.
Usually SMPS transformer is very tough so I had no idea about the reverse pull-down tester reading. I at once all the secondary diodes with my analog meter and found a shorted diode (part number U202G). Since I do not have this part number, I use a UF5404 ultra fast recovery diode as a replacement. In fact, I UF5404 this for all 14 to 17 "monitor as a replacement for each part number of the secondary diodes. 400Volt The specification of this diode was 3 amps at 50Nanosecond.
After replacing the diode, and placement of the flyback tester probes again points to the primary winding, the result of full bar on the LED. Do not be satisfied with the result, as has not done your job.
Then I went to examine HOT with the same procedure as the control of the power FET. The HOT considered to be in order. Next, I check the internal capacity of the flyback transformer is shorted to see or not, or has the capacity to run value. For yourInformation, internal capacitor in the flyback transformer were many problems in computer monitor. I scanned through the B + FET and found it to be good, too.
Now is the time to switch on the monitor, but this round I Do not light, because it was just a shorted diode in the secondary. I would just compound in a light bulb after the repair, if major short circuit in the original page, such as a blown bridge rectifier, SMPS primary fet and short-circuited and burnedComponents to the board.
The Dell 17 "monitor works fine, and after long hours of burn-in test, I said, it's okay and ready to do it back to my loyal customers. Repair it can monitor and not funny in the end you get something that They like to make payment. I love electronic repair!
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