Adjustable Shunt Regulator Found Defective In LG Fridge Inverter Board
MAKE AND MODEL: LG SMPS INVERTER BOARD
COMPLAINT REPORTED: Dead
TROUBLESHOOTING AND RECTIFICATION DONE: The board was brought by a AC technician and the board was clean enough for me to do the troubleshooting straightaway. Checked for any residual voltage in the two tank capacitors. Removed the Heat Zinc of the Three Phase control IC No.SIM6822. Used my ring tester on the SMPS transformer and found it to be ok, with full LEDs glowing.
Powered the SMPS and found that the output is oscillating, i.e., on/off, indicating either a secondary overload or problem in feedback. So, disconnected the power and discharged the caps. Then looked at TL431 IC and found it to be strained. The technician had already told me that a 1000/25V cap in the secondary was getting warm. Replaced the TL431 and this cap and then applied power. Found the board to be working with the green LED lighting up. It was an indication that the board is now functional. Checked the output voltages and found these to be present. The board was picked up by the technician, who reported later that the Fridge was working. Mission accomplished and satisfaction of a different kind got collected!
HERE ARE A FEW PICTURES:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 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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