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DVD Player No Power But Not Power Supply Fault
This MAPS DVD player came in for repair with the complaint of no power. As usual, when an equipment is no power the first thing to check is the power supply section. The best point to test will be the output points or the connector points. When I checked on the output points I found 5 volt and 12 volt were present. This proved that the power supply was working and the fault could be in the mainboard.
From my experience in DVD player mainboard troubleshooting, the first components to check would be the transistors and the diodes.
You also need to know that if the flash Rom firmware is corrupted it will also cause no display in the front display and you may be thinking it was the power supply fault.
The transistor part number was S-8550 and both were tested good.
However, the diodes seems to be opened circuit.-see the photos below:
I took out the new diodes (1N4007) from my compartment and soldered it behind the mainboard just to test if the mainboard will come to life or not.
To my surprised, the DVD player was playing normally again as seen from the photo below. Usually the diode is either leaked or shorted but this round it was open circuited.
Conclusion- If all the four components were tested good then I will check on the Crystal oscillators and the surrounding DC supplies to all the ICs. I may even look for the flash rom original data. If you want to learn DVD player like a professional please check on Humphrey’s ebook here. Hope to see you again in the next repair article.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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