LED Bulb Repair

Joshua R. T. Purba
Electronics

I have an old, broken, cheap LED bulb. It broke some time ago. I’ve diagnosed what was wrong with it but never actually repaired it, until today.

Popping open the diffuser was easy. Inside the problem was immediately clear. The electrolytic capacitor had exploded. Other than that one of the LED was open circuit. I tested all the LEDs using my multitester and everyone lit up except the broken one. The 0.82μF 400V polyester film capacitor on the back seemed OK.

Externally you can't tell what's wrong with it.

The broken LED bulb.

See the small dark spot on the topmost LED? I think that's where the bond wire burnt out. Notice the two through hole on the left for the electrolytic capacitor had been desoldered. I desoldered them a long time ago. The dirty flux residue wasn't from me. It was already there.

The topmost LED is broken.

The electrolytic capacitor had exploded. The top of the casing was bent. The capacitor's bottom black rubber plug had been pushed out by the explosion. There were bits of its insides everywhere, not in this picture because I have cleaned them.

The electrolytic capacitor is broken.

I had desoldered the electrolytic capacitor some time ago. Today I desoldered the LED and that was difficult. This broken SMD LED’s plastic body easily melt when touched by my soldering iron tip.

I only need one replacement LED, but there were minimum order quantity of 5. The replacement electrolytic capacitor has the same rating with the broken one: 47μF 50V. In hindsight I probably should have ordered a higher voltage one.

The replacement components.

The broken LED had been desoldered, and the pads had been tinned. I also cleaned all flux residue that's been there from the factory.

The broken LED had been desoldered.

I made sure the replacement LED still worked after I soldered it.

The replacement LED had been soldered.

The replacement electrolytic capacitor had been soldered.

The replacement electrolytic capacitor had been soldered.

After soldering the replacement LED and electrolytic capacitor I tested it using the mains current limiting rig but not the way I intended to when I built that rig, as in this time I don’t use it to limit current. After initial test without diffuser went fine, I popped the diffuser back on, retested it and everything still went OK.

I can't remember whether this was with or without the diffuser. It worked though. It drew 52mA from mains.

The LED bulb lit up OK.

Just like that this cheap old LED bulb can be used again.

See you later folks!