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How To Repair Fish Tank LED Light Bank (With Video)

By on June 18, 2018
testing led lights










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.

fish tank led light repair

This light bank used 2 separated power sources, one for the blue LED’s and one for the white LED’s.

power supply adapter repair

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.

led light arrangement


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.

  1. Using a digital multimeter on the diode function, which lit the LED slightly
  2. Using 2/ 1.5 Volt batteries in series to supply voltage to individual LED’s

how to test LED light

The faulty LED was quickly identified and a replacement through-hole was temporarily held in place to prove the repair would be successful.

testing led light

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.

how to fix led problem

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.

automotive sealant

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.

shark and jaws photo

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:




  1. Parasuraman

    June 18, 2018 at 10:54 am

    That was a 'fishy'fix!() Good info! Thanks for sharing!

    • Mark

      June 18, 2018 at 5:58 pm

      I thought something was fishy as soon as I started the repair!

  2. Robert Calk Jr.

    June 18, 2018 at 3:33 pm

    Good job, Mark.

    Also, for anyone that is interested, there is a new update available for the Peak Atlas DCA75 Pro:

    I talked to them a few weeks ago and asked if they could update the analyzer to test a PUT (Programmable Unijunction Transistor), but it isn't in the new update. Hopefully it will be in the next update.

    • Mark

      June 18, 2018 at 5:59 pm

      Thanks for the update!

    • Albert

      June 19, 2018 at 10:58 am

      Thanks Robert. Its only an PC software update. F/W DCA75 still version 0021.

      • Robert Calk Jr.

        June 20, 2018 at 4:46 am

        Thanks Albert. I never said it was the greatest update in the world...

  3. Albert

    June 18, 2018 at 9:47 pm

    Nice drawing Mark. And well explained! Although the drawing of the led lights somehow does not exactly match with the blue and white colors on the photo?

    • Mark

      June 19, 2018 at 11:56 am

      You are probably right. I just did it in Word and didn't focus too much on the photo. I was trying to explain series and parallel circuits because I think I made a mess of the drawing on the video!

  4. Henrique Jorge Guimarães Ulbrich

    June 18, 2018 at 10:04 pm

    Good, Mark. An excellent video too. Thanks for sharing.

    • Mark

      June 19, 2018 at 11:57 am

      Thanks for your comments 🙂

  5. Henry

    June 19, 2018 at 10:53 am

    Nice article and video, Mark. I like your style. I am from Australia and probably from the same city too. I do some electronic repairs on a smaller (hobby) level but too often face problems with the availability of the components. I wonder how and where you get the required parts/electronic components from.

    • Mark

      June 26, 2018 at 10:16 am

      Hey Henry,

      I live in Goulburn, NSW.

      I get most of my electronic parts from RS Online or Jaycar.

      Other places I get white goods part from are listed below.

      These offer freight of some description (RS Online offer free delivery, regardless of the purchase as long as it is done online)

      I hope that helps

      • Henry

        June 27, 2018 at 2:31 pm

        Thank you Mark for the info. I am in Sydney. We have here Wagner Electronics and I used them before but without much success. Next time perhaps I will try RC Online.
        Looking forward to more of your articles and videos.

        • Mark

          June 28, 2018 at 7:42 pm

          Cheers - glad you like them! 🙂
          I use RS all the time and although they aren't the cheapest around, their service and delivery make up for any extra expense.

  6. Humberto

    June 20, 2018 at 5:12 am

    Hi Mark, great article. I'll watch the video later.

    • Mark

      June 26, 2018 at 10:20 am

      Thanks for your comments

  7. Dan

    July 15, 2018 at 9:32 am

    Thanks for the info and demonstration. It helps me to understand more.


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