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7N65C Power FET Shorted In Singer Hi-Fi DVD
The complaint of this Singer HiFi DVD was no power. Once the cover was removed I managed to see three circuit boards in it.
It was the power supply board, Main board and DVD card-see the photos below:
Since the complaint was no power so I had to check on the power supply board first. The first thing to check is the main fuse and I found that the main fuse was dark in color indicated there was a serious short circuit in the circuit board.
I checked on the bridge rectifier and components corresponding to the EMI filter and found no shorted component. Next test was the main power fet. I checked it with my multimeter set to Ohm and found that the three pins power FET was shorted. It showed very low ohm-see the photo below:
The shorted power Fet part number was 7N65C. I continued to check for bad components and did not find any. My conclusion was only two bad components- bad fuse and power fet.
I did not straight away put the components and power it On, in fact I connect the series light bulb method to make sure there is no longer short circuit. The bulb was bright in the beginning due to capacitor charge and after that it went off. This is a good sign that there was no short circuit and I can put the main fuse and power it up.
Once the powered was on the Hi Fi came back to life and I was very happy because I can make some profit from this repair work.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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