Blue Ring Tester Result
Today I am going to share one of my troubleshooting experiences with Blue Ring Tester which I have bought from Mr. Jestine Yong. There was a problem with one SMPS which was dead and not showing output voltages. The SMPS was a 12V 120Watt and used as LED power supply.
One of my customers came to my office and told me that the SMPS was not working. After testing the SMPS I found the main fuse, bridge rectifier and power FET was shorted. After replacing all the components I used the series light bulb trick and the bulb was brightly lit and this means there was still short circuit in the board.
I suspected the main filter capacitor but after replacement the problem was still the same. My next moved was to check on the SMPS transformer primary winding. The Blue Ring Tester showed full LEDs and this means the SMPS transformer primary winding was good. When I checked on the secondary winding I found that it was open circuited causing the bulb to light up.
Here is how I have checked the transformer:
I removed the bad Switch Mode Power Transformer (SMPT) and compared with a good one. I checked it the way as mentioned in the Switch Mode Power Supply Ebook by Mr. Jestine Yong. First, I checked the primary winding of the transformer and found the winding to be good as shown in the below photo (8 full LEDs lighted up).
Then I made a short between pins in secondary winding with Long Nose Plier and there was no effect on LED bar of Blue Ring Tester. Please see the photo below:
Note: A good transformer when shorted the secondary pins, the Blue Ring Tester LEDs should go off or one or two LEDs should be blinking. Please see the photo below:
All the 8 LEDs went off when shorted the secondary pins with a long nose plier
A replacement with a new SMPT brought the dead power supply to life again.
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