Device: MIBOXER Touch Screen LED RGB Controller
Issue: Device was wired up with positive and negative power reversed. A small explosion and release of gas occurred resulting in loss of functionality. The box states that if this happens "the controller will be broken."
An inexpensive and rather cool device, this controller makes use of the Mi-Light RF protocol to control LED tape via touch screen remote control.
This controller was bought to be used inside a custom-built postbox to make the letter opening glow various colours. While the LED was being installed this box was continually connected and disconnected to troubleshoot. In doing so it was accidentally supplied power in reverse polarity and with a dramatic bang it stopped working. All RGB outputs stayed at full with no response from the remote.
Using a screwdriver to carefully open the tabs on the case I was able to see what had happened.
Cracking open the device
Exposing the circuit board revealed a host of issues. From the picture above you can see loose debris where components have literally exploded, and residue from the a capacitor.
Naturally the first step was to replace what had broken. Closer inspection revealed that the debris was from a diode on the output side and the bulged top of the capacitor was obvious.
Metering out continuity from the remaining diodes in-situ provided inconsistent results, and since the replacements came in packs of five, I decided it best to just replace all 3.
You can also see that the copper lane near the diodes has also been scorched away. This would need to be fixed with a solder bridge.
Damage can be observed in the upper right corner of the board.
Once everything was replaced I connected it back together again only to find that the red channel was unresponsive and stuck at full. Having encountered a similar problem when fixing my DMX 512 decoder I immediately suspected a malfunctioning transistor. Not being able to find an exact replacement, I noticed that the transistors used in the aforementioned project had similar specs and so decided to try one here. Success! I had now regained full control of the device
While the controller may have only cost £8, there was some satisfaction for fixing it for under 50p.
Issue solved!
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