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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https://jestineyong.com/no-power-in-telesonic-dvd-player-solved/
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Leave a Reply
Angelo
July 28, 2017 at 8:45 am
Sir Suranga
i love reading ya article
u always save time by directly coming to the main point..
Love ya
keep blessing us this way by ya experiences...
Thank ya
Parasuraman
July 28, 2017 at 8:59 am
Excellent expert approach straight to the problem!
Kushan
July 28, 2017 at 9:28 am
Thanks for sharing this Suranga, you have done it clearly with few steps..please share many with us
Suranga Electronics
July 30, 2017 at 11:02 am
Thanks Mr,kushan.
Yogesh Panchal
July 28, 2017 at 3:32 pm
Good job! Suranga,
which legs are shorted of FET let me assume Drain to source?
Albert
July 28, 2017 at 9:24 pm
Good repair Suranga! Any idea what caused it?
Thanks.
Robert Calk
July 28, 2017 at 11:12 pm
Good job, Suranga. It looks like you soldered the test light wires to the fuse holder. I put insulated alligator clips on my test light wires to make using it much quicker and easier.
George Persico
July 29, 2017 at 1:43 am
Suranga, nice clear troubleshooting steps. We should also note the reason the fuse turns black for those learning. When an overload is just slightly above the rating of the fuse the fuse goes open WITHOUT the black color. However when the overload is severe MANY amperes are drawn through the fuse which vaporizes the fuse wire, causing the black deposit inside the glass.
Again, nice job
Mahmoud
August 1, 2017 at 6:49 pm
well done
Humberto
August 6, 2017 at 12:59 pm
Good job Suranga, as usual
Ulises Aguilar Pazzani
August 21, 2017 at 12:55 pm
great Job Mr Suranga
Ulises Aguilar Pazzani
August 26, 2017 at 12:09 pm
Mr Bandara good job Sir
Steve Griffin
January 16, 2018 at 6:30 pm
Nice fix. I am looking forward to a proper explanation of How the "light-bulb" is connected to show working status. I have heard this test before and like how this method is so full of information if something further is wrong. Very clever! I am liking these Audio/Hi-Fi repairs. ThankYou! Suranga.