How To Repair Fish Tank LED Light Bank (With Video)
One of my students asked me to have a look at his fish tank light bank, which consisted of LED’s as the light source. Only some of the lights had failed and he was unsure about the testing procedure. After inspection, it could be seen that all the blue lights were working on both the bottom and top banks; however, the white lights were only working on the bottom bank.
This light bank used 2 separated power sources, one for the blue LED’s and one for the white LED’s.
The first power supply provided between 45-55 VDC at 1.36 Amps and the second provided 18-42 VDC with 500mA of current.
Although I did test both power supplies, it really was unnecessary as both blue and white lights were working. This is where an understanding of parallel and series circuits helped with the diagnosis.
Here is a very rough schematic of the light bank. Please excuse the drawing – I didn’t have time to paint it or draw it to scale (sorry, a ‘Back To The Future’ reference…)
Both power supplies are in parallel to each bank, supplying the correct voltage to both the blue and white lights. However, each LED is in series with one another. Therefore, since only the top bank of white LED’s were not working, it could be diagnosed that something had interfered with the series circuit – most likely a blown LED. Simple.
Testing required that all the white lenses on the top bank be removed to gain access to the LED connections.
Testing was done using 2 methods, just for teaching purposes for the video.
- Using a digital multimeter on the diode function, which lit the LED slightly
- Using 2/ 1.5 Volt batteries in series to supply voltage to individual LED’s
The faulty LED was quickly identified and a replacement through-hole was temporarily held in place to prove the repair would be successful.
When the replacement SMD LED arrived through the post it was soldered in place, ensuring it was installed with the correct polarity and some thermal compound was applied to the back of the LED to promote heat transfer.
After the repair was completed and testing carried out, it was time to refit the LED lenses. I was unsure of what type of adhesive to use to hold them in place, but after some research, the most important requirement seemed to be that it be non-corrosive.
Since I am an Automotive Technician by trade, I decided to use a silicon based material that promises to be non-corrosive and that I could use in my normal repair work as well. With all the lenses now firmly fixed in place, I carried out one final test before handing the light bank back to the customer.
He assures me that the fish are now very happy that they have their repaired light bank back again.
If you are interested in this repair, you can see a video on my channel following the link below:
This article was prepared for you by Mark Rabone from Australia.
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Note: You can check out his previous repair article below: