QuestionQUESTION: First it was power on and works fine but press POWER button will not turn it off! So I have to unplug the power cord to turn it off.
Then when I re-attach power cord, it will not turn on, only have standard by light.
Finally it is totally dead,not have any light, no matter press POWER button or press CD + POWER. All the fuses are good, and The electricity is good. (Inside I tested it has 120V Ac power)
Please help! Thanks a lot!
ANSWER: It is a very old set. So, you must expect some trouble along the way.
My first guess is the power supply has gone into protection mode. This is caused by excessive currents being caused by something in the amp that placed a heavier than allowed for loading which triggers the protection mode circuit.
One of the causes is from an electrolytic capacitor inside the power supply. They are easy to replace. Look at them carefully and if you see any bulging or electrolyte oozing out of its case that is a top clue to trouble.
So, take a look at that and let me know if you are still stumped.
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QUESTION: Thanks for your answer, however I am still stumped.
I took the only capacitor out of the board it is a 220uf 16v one.
It looks normal, plus tested good(I used multimeter to test).
So I am going to put it back.
Is there any other element may cause that "protection mode" permanently?
(When the speaker were not connected, there were no excessive currents any more but the receiver is still not turn on when press power button)
AnswerThat is a clue; with speakers disconnected and seems normal operation then it may be one of the power output or more are burned out. Do you know how to test for that? Easiest way is if you can get the amp to stay on for long enough period of time and speakers disconnected measure dc voltage at output junction of the push - pull power stage. If way negative or positive it is usually a sign of a shorted transistor. Or, you can pull the connections and test the transistors with the vom.
Maybe this will help.
