12V Power Adapter Compatible with Roland Electronic Keyboard

A 12V charger with the 5.5x2.1 barrel connector is one of the most common and basic power supplies. It is bundled with many external hard drives, routers, pictures frames, you name it. This one has the maximum current stated at 2A, which is not anything special, given that many drives nowadays are shipped with a 3A wall wart. However, this one was indicated to be used for pianos, so I assumed it can be better characteristics as electrical noise not to interfere with the sound. So I tested it. Without the load the power supply outputs 12.2V. This is good. Electrical noise was higher than it is for similar power supplies (not good). I measured it to be around 270mV without load and around 450mV at 2A. That's almost 4% which exceeds a generally acceptable 1-2%. Loading the power supply can be temporarily done up to 4.6A, which is exceeding twice the stated limit. At this load, the voltage drops to 10.2V and the efficiency will be 63%, which is low and will generate a lot of heat at the power supply. This small power supply will try to dissipate almost 30W in heat. Fortunately, some thermal protection kicks in after a minute and the power supply shuts down for a second before restarting. I kept lowering the load and the power supply was shutting down, after a few minutes, which is generally good and shows that some type of protection is working. However, at 3A load, the power supply was not shutting down and kept working increasing the temperature. The efficiency at 3A is 75% and it generates 11W in heat. The temperature on the surface kept on climbing and exceeded 99 degrees C, which is way too high and it wasn't insulated. This supply really was becoming a fire hazard. The power supply was open from all sides and I rant the test for about an hour. While it didn't fail nor melt, having the surface temperature at one spot over 90C is too much for an electronic device that doesn't try to burn the house down. Overall, if you are absolutely certain that the load will not exceed 2A, this power supply will be OK. However, if you are not certain or your device can exceed this limit, get a different power supply with proper protections.

My charger came in perfect condition, very quickly. Worked with my large keyboard and my kiddos smaller one which is cool. Perfect purchase, would purchase again. Thank you!