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This DELL 17鈥? Observe (Made in Malaysia beneath LIKOM model L705XXX, solution no: L7055LP) came in without the need of power symptom. Normally after opening up the cover I would think about the power supply (primary side) to get a burnt and cracked equipment first. If there will be darkened area and burnt off components, I would tell myself that Monitor needs somewhat more time to repair it all. If it is not (component鈥檚 intact) We usually begin to eliminate the filter capacitor you need to checking the fuse. Acceptable, it is confirmed that most the primary side components looks good in such a Monitor. First, discharge the big fat filter capacitor using a resistor (I know the fact that voltage already drained off but this can be a normal procedure for me because imagine the start up resistor comes with open circuit? ) subsequently check the fuse. Should the fuse is okay, experience will explain that the bridge diodes may also be working fine. Place your black probe of one's analog meter set to x1 for the center pin (drain) of your power FET and red probe with the other pin individually (gate and source). Should the pointer of the meter doesn鈥檛 end then 80 % with the Power FET is acceptable. If you want to 100% confirm whether it's good then you need to solder it out and additionally test. If the pointer presents a reading then most likely the power FET has changed a short circuit. The results that I got made by this Monitor was the pointer don鈥檛 flick. <! --INFOLINKS_OFF-->
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The time has come for me to use a dick smith flyback tester to examine the smps primary rotating. The result that I obtained was, the led pub don鈥檛 lit. Ah ha! That was a clue this clue tells you it's either the smps principal winding is shorted or one of many secondary diodes has specified way. Of course you can examine all the secondary diodes with the normal multimeter first (remember, every electronic repairers have their particular procedure methods of troubleshooting) but I favor this way as I must confirm also if your smps primary winding might be working or not. Usually smps transformer can be quite robust thus I didn鈥檛 suspicious it to pull affordable the flyback tester examining. I straight away check every one of the secondary diodes with great analog meter and discovered one diode shorted (part multitude U202G). Since I do not need this part number, I use a UF5404 extra fast recovery diode as an alternative. In fact I utilize this UF5404 to all 16 to 17鈥? Monitor as an alternative for all part variety of secondary diodes. The spec in this diode was 400volt, 3 Amp having 50 nanosecond. After the replacement with the diode, and placing the flyback tester probes again towards primary winding, the result shows full bar around the LED. Don鈥檛 be satisfied with the result yet because your task still hasn鈥檛 done. Now I got over them to check HOT with all the same procedure as checking the facility FET. The HOT checked for being okay too. Next, I check the interior capacitance of the flyback transformer to find out it is shorted or not or is definitely the capacitance value run. On your information, internal capacitor in flyback transformer gave many problems in computer Keep an eye on. I also scanned through the B+ FET and found it for being good too. Now could be the time to switch within the Monitor, however this round When i don鈥檛 connect any bulb because doing so was only a shorted diode inside the secondary side. I would only connect a lamp after repair travellers have the major short circuit with the primary side for instance a blown bridge rectifier, shorted fet and smps primary winding and as well burnt components in all the board. The DELL 17鈥? Monitor worked beautifully and after extended hours of burn-in test, I declared it okay and wanting to send back to my personal loyal customer. Isn鈥檛 it fun so that you can repair a Monitor and by the end you get paid for something you wish doing. I just like electronic repair! <! --INFOLINKS_OFF-->.
