LG Mini Hi-Fi Repaired
Customer sent in this LG Hi-Fi with the complaint of standby mode. I tried pressing all the front control button and there were no response at all. Even with the remote control would still not be able to bring the power up. This concludes that there was a problem in the internal part in which I have to troubleshoot and find out the culprit.
The below photo is the main control board that consist of CPU and sound amplifier section.
Visual inspection did not see any unusual problem in the main control board thus I focused on checking the standby voltage. I checked all the voltages seems to be within the specification but one thing I noticed that there was no stand by voltage.
I took out the front panel display PCB (two photos below) and checked on all the micro switches for short circuit and leaked.
If one of the micro switches is stuck and On all the time this can cause some weird problems including the standby mode.
Since I have many micro switches, I replaced all of them and retest the set. To my surprised the set came back to life again. See all the photos below:
Conclusion- You can never under estimate what a malfunction micro switch can do to your system/device. A leaky, jammed or intermittent micro switch can cause many different kind of problems in the system because the front panel control board is usually connected to the main PCB board.
Anything that goes wrong in the front panel board may have serious implication on the main PCB board. It is always good to keep some spare micro switches (few types) if you do lots of repair work. Ok, will see you again in the next article.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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Note: You may check out his previous post about Haier 50 Inch LED TV With No Power Repaired
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Parasuraman S
July 23, 2022 at 7:54 am
Excellent! Yes, I do agree! Front Panel control switches do cause many funny problems due to internal leakage and otherwise!
Raj
July 23, 2022 at 9:30 am
Great.. Thanks
Tito Kanshulu
July 23, 2022 at 1:08 pm
Nice repair Suranga. Quite interesting to learn about stuck microswitches. It's a thing most technicians never think of
Albert van Bemmelen
July 23, 2022 at 2:56 pm
It indeed is always good to have spare parts in stock! Which also is a repairman's dilemma because it requires lots of extra storage space and spend money.
Waleed Rishmawi
July 25, 2022 at 2:24 pm
yes, a very good idea to replace all of them. many techs they just spray cleaning liguid in there but sometime that is not enough. a very good repair article and thanks for sharing. have a blessed day
Bill
July 26, 2022 at 4:25 am
I would have sprayed all the buttons and tried it again. But after it worked, I wouldn’t know which one was the bad one. That would’ve certainly left the possibility of it just happening again. Good idea to replace them all.
Yogesh Panchal
July 30, 2022 at 11:36 pm
Good Job! Suranga