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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You may check on his previous repair article below:
https://jestineyong.com/bridge-rectifier-found-open-in-iball-computer-smps/
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HECTOR DELATORRE
August 19, 2020 at 9:08 pm
How did know check the TL431
Parasuraman S
August 19, 2020 at 10:16 pm
I have mentioned that I found it to be strained. In SMPS, one of the reasons for oscillation is feedback defect. That's why I replaced the TL431.
Josh
August 20, 2020 at 12:09 am
How do you mean ..Strained?..
I enjoy your posts!
Waleed Rishmawi
August 19, 2020 at 10:00 pm
you found the fault and confirmation by the AC technician completed the repair. good job my friend. have a blessed day
Parasuraman S
August 19, 2020 at 10:17 pm
Many thanks, my dear friend!
Robert Calk Jr.
August 20, 2020 at 3:05 am
Good job, Parasuraman! My sisters large upright freezer quit working a few weeks ago. The technician told her that the compressor was out. It was only a couple of years old so I did not believe him.
I repaired it with a $10 thermostat that they call a Cold Control. I saved her from buying a new freezer!
Parasuraman S
August 21, 2020 at 10:15 pm
Vow! That's a great deed indeed, that too for own sister! Double achievement!
Raj
August 20, 2020 at 9:07 am
Great tips.. thanks much Sir..
Parasuraman S
August 21, 2020 at 5:32 am
Many thanks!
Albert van Bemmelen
August 21, 2020 at 12:22 pm
Great job and nice to see that you didn't first have to clean the defective inverter board!
Parasuraman S
August 21, 2020 at 10:12 pm
Ha! Ha! Many thanks for your comments!
Parasuraman S
August 21, 2020 at 10:13 pm
Ha! Ha! Many thanks for your comments!
Yogesh Panchal
August 24, 2020 at 12:24 am
Good Job! Sir,
Henry
August 24, 2020 at 10:20 am
Good and effective repair and only one e-cap replaced this time. However, I do not understand the statement "TL431 IC found to be strained" in your diagnostic process. Could you please explain what test measurements you performed and what indicated a "strained" TL431?
Humberto
August 27, 2020 at 12:46 pm
Good repair, Parasuraman. These Fridge Inverter Boards are put on the shelf by the Techs in my country, and none of them want to repair them. It´s a pity
Dan Stark
August 31, 2020 at 5:06 am
what do you mean by the word strained? in the article: Adjustable Shunt Regulator Found Defective In LG Fridge Inverter Board.