Restored A Lovely LED Surface Panel Light
This LED light belonged to my colleague in the hospital and was brought to me with the complaint that it was found dead. I checked the LED drive and found it was producing the required voltage. So, the culprit was the LEDs. In order to open the lamp, you need to pry open the ring on the top, which are locked to the metal case.
After opening and removing the glass, mask and ground glass type plastic sheet which distributes light evenly (I am not sure of the names I used to describe!), I removed the led strip stuck on the inside.
The inside of the LED driver:
I checked the strip applying voltage from the LED tester, which showed the LEDs were short. Just out of curiosity I counted the LEDs and used my LED Tester to find out the burnt out LEDs and the voltages of the ones that were ok. Found a few LEDs shorted.
Though replacing just only the defective SMD LEDs was possible, I opted for replacing the strip, as other LEDs would also fail one by one soon. Got the replacement strip and checked it with my LED tester and found it to be alright. Peeled off the gum protection and stuck the LED strip firmly inside the slot in the original place where the other was.
Before connecting the LED driver, I did a retouch of all the soldering points and also replaced the two electrolytic capacitors; 6.8uF/400V with 10uF/450V (as I was not having 6.8uF) and 3.3uF/250V with 4.7uF/250V (same reason here too). Cleaned the board thoroughly with IPA. Applied power and checked the voltage output before connecting the LED strip.
Used the soldering iron from my newly added replacement SMD re-work station Kada 2018D+ and connected the +/- wires to the LED strip. The thin bent tip was found very useful for a precise solder:
Applied power and found the LED strip glowing very brightly. The voltage measured was 56V DC. It was safe enough. Fixed the glasses like before and pressed the holding ring to its locks.
Needless to say that the mission was accomplished very well and satisfaction got added to its collection bag.
Special notes: (1) Never ever replace part of LEDs in any LED strips, as the current drawn by new and old might vary and either the other LEDs or the ones replaced would soon fail, making a revisit, leading to customer dissatisfaction. (2) Always spend some time studying the defects thoroughly to know more about it, as part of our progressive education. (3) Always take snaps and note down the step by step troubleshooting done for easy reference later, as and when found necessary.
This article was prepared for you by Parasuraman Subramanian from India. He is 72 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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You may check on his previous article on Complex Circuit Of Panasonic Surround System SA-PT860 And Tips For Troubleshooting