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Not Common To See Dual Super Barrier Rectifier Breakdown When Under Load
The complaint of this LED TV was no power so the first thing I did was to check the output voltage of the power adapter.
It was rated as 12 VDC and when I measured the output jack of the power adapter I got 12.1 volt which mean it was good -see the photo below:
When i checked on the connector of the dc 12 volt supply in the circuit board I was surprised to see the voltage was only 3.6 volt. It suppose to be 12 vdc and not 3.6 volt.
This means the problem can be caused by either the circuit board itself or the power adapter. In order to confirm which section is giving the problem i have used an external 12 vdc to plug on the circuit board-see the photo below:
It shows 12 vdc and I could see that the LED TV screen was working (see below photo). This concluded that the power adapter is the cause of the problem. It also means that the power supply can’t sustain the current draw by the circuit board causing the 12 volt to decrease to 3.6 volt!
Next, I opened the power adapter and see if I can find some bad components in it. The filter capacitors were checked to be good and there were no sign of burn components too. All components were intact.
Even the dual schottky diodes was tested good when checked with my digital multimeter
Below is the Dual Super Barrier Recctifier datasheet:
Since I could not find any bad components in the power supply, I directly replaced the dual super barrier rectifier and retested it again. I was a bit surprised to see the voltage came back to normal again (11.6 volt) and the display appeared-see the photo below. It had never came to my mind that a dual diodes could breakdown when under load.
Conclusion- Sometimes one just has to direct replace a component and retest the set because a component that is breaking down when under load is hard to be detected by a normal meters.
All the best!
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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