Today I’ll show you how you can repair a broken LED light fixture.
Tools and materials needed (affiliate links):
Soldering Iron: http://s.click.aliexpress.com/e/b6P0bCRI
Solder Wire: http://s.click.aliexpress.com/e/bBmvoCmk
Wire Snips: http://s.click.aliexpress.com/e/bTDNevoM
Assorted Resistors: http://s.click.aliexpress.com/e/bb3P6qJW
Assorted High Voltage Capacitors: http://s.click.aliexpress.com/e/bJtOowDE
Step 1: WARNING: Mains Electricity!
This project involves dealing with mains voltage! Extreme care should be taken if you want to attempt a similar repair. If mishandled, mains electricity can kill you!
Step 2: Diagnose the Problem
I had this LED light mounted in my home and it recently stopped working after a problem I had with a loose ground wire. I already replaced it with a new one but I wanted to see if I can repair this one and use it in my workshop.
After I opened up the casing, I immediately saw this burnt fuse resistor. The resistor is 2.1 ohm with at least a half a watt rating so I started searching for a replacement. The closest one I could find was this 2.2 ohm resistor but it was in a much larger form than the original and I didn’t wanted to allow the fixture to fail at larger current.
Instead I used two 7.2 ohm, ¼ watt resistors in a parallel configuration to get about 3.5 ohms with a half a watt rating as a replacement.
Step 3: Try Your Fix
After I removed the leads from the old resistor I’ve inserted the new pair through the same holes and without further inspection I was eager to try the lamp out. I connected it with some jump leads to a mains plug, making sure to isolate all of the jump wires connections for safety.
After plugging, I heard a pop and the light didn’t came on, so I knew that I had some other issue as well and I should have checked better. Reviewing the footage later, revealed a nice small explosion on the resistors that I just replaced.
Step 4: Diagnose and Fix - Again!
I removed the light from the mains connection and continued with further inspection. What caught my attention is this smoothing capacitor that was across the input on the bridge rectifier as it had some discoloration. I removed it from the board and sure enough, the capacitor had a crack on one of its sides.
The capacitor was labeled as 470nF and the closest I could find from my old electronics pile was a 330nF from a broken compact fluorescent lamp. When replacing such capacitors it is crucial that you get a replacement that is rated for the voltage that you are working with. This one was rated for 400V so I knew that it will be good enough.
I then replaced the capacitor and once again, replaced the resistors on the input. I now made sure to do some other tests on the board for any shorts or other weird readings and after I was sure I could not find anything else that was broken I connected it again for testing.
Step 5: Success!
Sure enough, I had a success. The light started working and even though it looks flickery on camera it produces a nice light in person. I then set to isolate the driver board and proceeded with assembling it back to its case.
Once everything was back together, I tried it one more time to confirm that it all worked.