Thursday, June 3, 2021

LG home theater model LHD657 came in with S-protect symptoms now Repaired!

 I received this machine with the above symptoms in my shop a few days ago, I opened the machine and went straight to the audio amplifier which from my experience is the major cause of this error.

I noted all audio I.Cs were running cool and therefore did not suspect them to be the cause, I did thorough testing on the components around the audio amplifier and i bumped on one smd transistor which was dead short.

The transistor was labelled Q407(HY4C), from the data sheet I noted the transistor was a PNP, getting it was not easy and therefore I decided to use an ordinary transistor A1015.

After replacing the transistor, I powered the machine and the s-protect was gone, i did intense testing and noted the new transistor was getting too hot and therefore decided to use transistor B892 which has better specs.

After replacing it with a transistor B892, I tested the machine for thirty minutes and the transistor was running cool.

Thank you guys


See you in the next class.




  1. Congrats and thanks for sharing. Come to think of it, I have trouble dealing with smd components and they have denied me successful repair on many occasions. Like right now I have subwoofer am working on and it appears power ic problem and when I try to Google it's part number I get no match. Thinking of putting universal power module. By the way I need wearable lens with light to see small smd components. Any idea how to get it?

    1. Connect me on my phone we sort all these issues my friend Takisi, you have my number as my former student.
      Regards Humphrey