Multiple Faults In LG Hi-Fi System Repaired
This LG Hi-Fi system came in with multiple faults such as no sound, can’t change to other button function, CD not working, FM malfunction and etc. Since there are so many sections were affected, it seems the problem could be due to improper DC supply voltage in the power supply section. The moment the cover was opened I got a bit shock because the mainboard was infected by cockroaches…look at the photo below:
I checked on the power supply output DC voltages and all output were tested good and stable! This means the problem is in the mainboard.
I took the mainboard out and fully washed with chemical and dried it but the problem remained the same. Look at the photo below of a ‘cleaned’ board.
If the power supply DC output voltages were good and so many function in the system been affected this suggest that problem could be in the main IC or the Ram IC (yellow circle).
Since I have extra new Ram IC with me, I replaced it first and see how it goes.
To my surprised all the functions in the system came back to normal again! CD was playing fine, FM have have sound and etc.
Conclusion- Beside the power supply need to be working fine to power up the circuit boards, Ram IC is equally important in making sure all the functions in the system are working good. Assuming after replacement of RAM IC was done and the system still malfunction, I will proceed to focus on the main IC. I believe the cockroaches leftovers had caused problem to the RAM IC. What do you think?
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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Parasuraman S
January 28, 2021 at 1:01 pm
A very good informative article. In a sense, all these pests are our 'agents' who ensure that we, technicians, are fed! (LOL) Many thanks for sharing. As mentioned by you, the cockroach excretions and other dirt would have caused imbalance in the impedance of the set that caused failure of RAM. Luckily the program is not pre-loaded into this, because of which a blank replacement revived the set. But in some sets (like in LCD/LED TVs) partial programs are pre-loaded in this and if it goes, we need to load the program externally and fix the IC.
Yogesh Panchal
January 28, 2021 at 4:42 pm
Good job! Suranga ,
The M12L128168A is synchronous high data rate DRAM.Synchronous design allows precise cycle control with the use of system clock I/O transactions are possible on every clock cycle. allow the same device to be useful for a variety of high bandwidth, high performance memory system application.
Eric Rice
January 28, 2021 at 11:05 pm
Cockroach urine leaves a highly conductive film and will corrode even galvanized chassis steel. When left on smd components and traces it literally kills components upon power up. Always clean the devices and boards before power up to to reduce the chances of additional damage!
Albert van Bemmelen
January 29, 2021 at 1:49 pm
Great done repair job here! It is always a question mark why these Ram memory chips go bad like in USB Memory sticks. And apparently they contain 'dangerous' materials we are unaware of what exactly that is. As new USB memory sticks or SD cards always come with a warning not to throw them in the environment after they are no longer working to prevent polluting nature. And we know that the first SIP or DIP slot Drams on computer mainboards radiated alpha-rays. As a result of the way in how they were manufactured. This is probably also nano particles related (dangerous for breathing life)?
Mark
January 29, 2021 at 4:37 pm
Hey Suranga,
Well done on a great repair. It also gave you an opportunity to pull out the heat gun!