Music Keyboard No Power Repaired
The complaint of this music keyboard was no power. The power supply converts the input AC 230 volt to 9 volt DC output.
As usual, in order to see the circuit board inside, one has to remove the screw first and the screws were located at the back of the cover. It was quite straight forward to open such screws.
Once the cover had been removed, i could see two circuit boards. One is the main power supply board where it takes in the AC230V and convert it into 9 volt DC output. The other board was an audio amplifier sound board. Since the problem is related to power so I did not check on the audio amplifier sound board.
When I looked at the main power supply board, I could see two burnt resistors. There must be a reason why the resistors got burnt. I checked all the components in the power supply and found only TL431 IC shorted and the rest of the components were all tested good.
Although the resistors were burnt, I still could measure the value. If it is totally open circuit then it would be a problem to locate such value. I replaced the two resistors and with a new TL431 IC and powered On the set and it worked superb. You can see the two 7 segment LED display lighted up when the power was On. Another equipment saved from the dump.
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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Note: You may check out his previous repair article in the below link: