Today I was given a Harmony 659. The owner claimed the backlight had been giving him issues recently. It would sometimes stop working, but usually smacking it on any horizontal surface that was handy seemed to fix it. Now the backlight doesn’t work at all.
Step one: STOP BEATING THE REMOTE
Four screws and a few plastic clips later, I could see the backlight was of the ‘EL glow’ variety and looking at the design, I had my first suspicion.
The glow layer was floating above the circuit board and received connectivity at the bottom from a set of three contacts that were pressed into pads by the rubber membrane layer. Instantly I thought, “Well there’s your problem! There must be something wrong with one of those pads!” An hour later after rounds of cleaning and testing, the remote still would not glow. My multimeter confirmed there was indeed connectivity. Back to square one.
Okay brain, think. Electroluminescent material works kinda like CCFL in the way it usually needs an inverter of some sort to operate. This means somewhere near the pads there is probably some power processing going on.
Ah-ha! found it, but… everything looks normal. Hold up- what’s going on here?
Well now that explains a lot. A large, heavy, inductor on the board, might decide to break free on a surface mount. Especially if it were helped by a few G’s from repeated beatings.
Problem is, when it broke free, it took the solder pad with it. Putting a new pad back on there is probably more trouble than it’s worth. Looks like the circuit makes a “T” and runs to an unused pad just on the other side of the inductor. Excellent! Let’s prepare the pads and reroute the legs.
As you can see, I have the back of the remote handy to make sure I’m inside the lines. The components have to fit in the compartments on the back plastic. Also, I added a bit of hot glue as insurance to make sure it didn’t stress the remaining pads.
Now the couch potatoing may resume!
