I suspect the DC-DC converters inside the OBi.
A common failure mode of all switched mode power supplies is the capacitor(s) on the ouput of the high frequency rectifier losing a significant percentage of the original capacitance. The feedback control makes the input side (oscillator/pulse width modulator/switch) work harder to compensate. The higher currents can raise the elecrical noise which finds its way into other parts of the equipment (Example later.)
A slightly domed top end of the can and/or dried leakage residue around the base of the capacitor are often tell-tale signs that they are not well but lack of these is no guarantee that it is still good.
Eventually there comes a point where the capacitor is performing its task so poorly that the input side has reached the limit of what it can do to compensate. The output voltage begins to fall from its design value and the equipment becomes unreliable or fails to operate properly at all.
I've had and repaired this problem with several wallwarts, a HP branded (but Benq inside) LCD monitor, a Panasonic DVD recorder, a Sony Hi8 VCR, a powered car mount for a PDA. A Samsung TV also failed with symptoms consistent with the above - I had it repaired under the 3 year warranty so don't know for certain.
My Sony Hi8 VCR was a classic example. The initial symptom was very noisy sound when playing back some tapes. I spent quite some time faultfinding in the sound processing section. Unlike VHS, Video8 and Hi8 use FM modulated audio on a carrier. Then the Vacuum Fluorescent Display failed to come on. Voltage readings around that soon revealed they were all too low. They are generated by a separate little DC-DC converter under a metal screening can on a different board. On desoldering the screening the distress of a couple of electrolytics in there was immediately obvious. I replaced all the electrolytics in there whereupon the display came back to life and the audio was working perfectly. The increased level of interference from the DC-DC converter was confusing the circuit which determined if there was one audio carrier or two. It was replaying monto tapes as stereo and demodulating the non-existent second carrie, so introducing lots of noise.
The capacitors are tens of pennies. Unfortunately most wallwarts have welded cases. They usually don't put up much of a fight against a Dremel and once open, capacitor replacement is easy. However, resealing the case to an adequately high safety standard is another matter. It is absolutely imperative that the two halves do not separate while the user is attempting to unplug the wallwart. This may not be so likely in the US but the British style 3 pin plug can sometimes require significant force to extract it from a tight wall socket.
