AP2764AI Fet Shorted In Dell LCD Monitor
This was brought to my shop for repair. It is a Dell LCD screen and it was dead.
I could not find a model number on it. The only numbers I could find was this.
These numbers were revealed the moment I took the LCD stand off. As you can see four screws has to come off. Once I did that, this was revealed.
A well shielded LCD screen. Few flex cables were inserted in and it has to be unplugged in order to get the printed circuit.
This is the power buttons cable and it was not clearly seen and I almost ripped the cable off.
Another cable to be taken off before the actual board was revealed.
Finally I got to the board. It was an ok board, not too messy. A quick look for bad soldering joint or cold one but it was all fine. I took the board off and checked for voltages on the main capacitor without power plugged in. I want to see if the capacitor has discharged or not. Look what I found.
The capacitor was still holding charge which means one thing that something is shorted along the way and was not allowing this capacitor to discharge. I discharged it right away and looked for something nearby that was shorted. Right away I spotted this.
There was a shorted fuse resistor right next to the main capacitor.
Resistors do not just get shorted out, something else was wrong there and I have to find out.
I used my LOPT/FBT tester and it was giving me that something is shorted out. Another version of this LOPT tester is called as Blue Ring tester. Since the capacitor was getting power and holding the charge, that means, it is was fine.
Now, either the diodes or the Mosfet were shorted out. I soldered the pins of the mosfet and when I checked again look what I got.
My meter reading was in the green and this means the Mosfet is shorted. I took it off board and tested it; it was shorted out for sure.
The part number is AP2764AI. It is 650 volts and rated 9 Amp. You can take a look at the datasheet by clicking on the photo below:
The moment I replaced that along with the bad resistor, the LCD came back to life.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.
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