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Using an incorrect power supply with the wrong voltage, current type or polarity can instantly ruin an electronic device, possibly beyond all repair. That's what probably happened with the Buffalo Technology wireless router shown in this video. In simple terms: one BZZZZT! and it's probably too late. Demonstrated in this video is the technique of developing a theory as to what went wrong based on surroundings and behavior of the router when connected to power. I also noticed that I could hear the Buffalo power adapter entering overcurrent protection whenever it was connected to the router. In this case, the outcome is fortunate as the protection devices did what they should and in time to save the other electronics from any serious damage. The diode should be replaced to restore the reverse polarity protection. (It's quite possible that the diode just failed from age, but that I doubt considering the factors mentioned in this video and the fact that the antenna was also missing. It also seems doubtful due to the low operating voltage and current of this router.) Yet these little routers aren't protected from everything, especially overvoltage. There is no protection circuit for that. A client of mine had the cable company out to work on their equipment and power adapters for the modem (12 volts) and router (5 volts) got swapped. The modem simply didn't work, and the router was toast, probably within seconds. What can you do if you a have a device for which you don't have the power supply? Sometimes you can make an educated guess as to what is needed by looking at the area where power comes into the unit. The polarity and voltage ratings of capacitors, arrangement of board traces, presence of rectifier diodes or a packaged rectifier, or even a voltage regulator IC/circuit may all give ideas of *approximately* what the operating voltage and current type (AC or DC) should be. Simple devices (like a tape recorder) with a motor or actuator may have voltage ratings printed on the motor or actuator. These may also be used as a guideline. So too can the number of batteries a device takes (often 1.5V x number of batteries). A slightly riskier (but generally safe) technique on devices using a DC power supply (or batteries whose output voltage you can't determine) is to bring them the input voltage up slowly with an adjustable power supply until the device seems to work normally. It should then be observed to make sure that nothing is getting too hot or stressed in operation. This may also work on some devices that are intended to run from an AC input, but that's not guaranteed and definitely riskier. And of course...sometimes a manufacturer actually prints the voltage, polarity and current requirements right on the device! Look around. Be careful with the substitution of plug-in power transformers. While some are regulated and will put out the correct voltage (or very close to, as shown in this video) at all times, others are not and will put out a much higher voltage if unloaded or not loaded heavily enough. Test them using a meter set to the AC or DC voltage measurement scale as appropriate. Tags: uxwbill kitchen table electronics repair buffalo whr-g54s router dd-wrt wrong power adapter used reverse polarity disaster damaged shorted diode protection device
