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471k MOV Cracked In LED TV Repaired
This Haier LED TV with the model of LE22C430V was brought to me with a complaint that the customer heard a loud ‘Tick’ noise, as soon as it was switched on and it became dead. I opened the TV and did general cleaning. Removed the single board, which housed the power supply and other functions. Found the Fuse was blown. So removed it.
This is a cylindrical fuse in plastic body. Noticed black marks on the side of a rectangular filter capacitor, and found 471K MOV (Metal Oxide Varistor) cracked. Since this MOV was under the heat sink of Mosftet, I had to remove it from the board to take out the burnt MOV. Luckily, the markings were intact on the other side.
Cleaned the dark spots. Checked mosfet using Peak Atlas and found it to be ok. Put back the Mosfet. Checked for any other component failure in the power supply section. Could not find any. Since ESR checking of all electrolytic capacitors were also showed normal reading, connected a series bulb in place of the fuse and switched on.
Checked and found 12V was coming. Did not connect the panel at this stage. Since getting replacement of Fuse and MOV of this type and value was difficult, I connected an MOV that I had, which read CVR 275/07. For the fuse, I slid a 3.15/250V fuse in a sleeve, and soldered leads on both sides for placing it horizontally.
Fixed the MOV at the rear of the Board, instead of under the sink of Mosfet, for easy accessibility and to avoid removing the Mosfet again, in case of need. Fixed the Fuse in its place.
Connected the panel to the clip-on connector and slid the strip wire to the LED back light, AC in connector and speaker connectors to their locations on the board, applied 230V AC in through a series bulb. The TV showed no signal, an indication that all was well with the TV. Connected a Video input and checked. The picture was superb!
Fixed the front cover. In this TV, we have to remove the rear screws, remove the front frame, disconnect the connections to the panel and remove the panel, to access the board, as it is fixed on the rear cover. Then we have to remove the two screws of the board and disconnect other connectors to take out the board. You can also have a look at the PWM IC used, snap of which I took when I removed the Mosfet. It is hidden under the heat sink.
Tested the TV for more than one hour and found it to be working well.
Another job completed satisfactorily.
This article was prepared for you by Parasuraman Subramanian from India. He is 68 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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