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.