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I recently moved and didn't properly mark a couple of power supplies before I packed them up. I have a turntable and a pre-amplifier that both use 15v power supplies. One of the two power supplies outputs 15v 250mA and the other outputs 15v 550mA. The documentation for both devices just says "15v". I have done an exhaustive search online to see if I can find which adaptor belongs to which device, and have come up with nothing.

I'm at the point where I'm going to have to just guess. But both of these components are fairly expensive, so I'm concerned about using the wrong power supply and damaging the device. I'm not understanding exactly what the difference in mA means, and what is the risk of plugging the wrong one in.

Kate Stafford
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    First, see if the two plugs are compatible. If you get lucky, you can't plug a supply into the wrong device. If that doesn't work, try the higher current one on the turntable. Something with a motor will likely take more current than a "preamp". – Olin Lathrop Nov 04 '13 at 12:59
  • Look carefully at the polarity of the plug, it varies too. There should be a symbol on the power adapter indicating polarity. – jippie Nov 04 '13 at 14:21

3 Answers3

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You can measure the current consumption of both devices, powering from the bigger PSU. And then assign the bigger PSU to the device with higher consumption.

Also, you can describe the devices and post some model numbers, and/or pictures. Often it is obvious what device has higher consumption.

johnfound
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The short answer is yes, it could be dangerous - but probably only to the power supply, not your equipment. Lets say you have a 500mA load and you attempt to use the 250mA adapter, then you will either overheat the 250mA adapter, or in the worst case, the transformer core in the adapter will saturate, cause large pulses of current to be drawn during the peaks of the mains cycle. In this case the mains fuse should trip. A tip: if one power supply is heavier than the other, it is probably the 550mA supply.

mr_js
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mA is how much current the device is drawing from the PSU. The first power supply is capable of supplying enough current for a 250*15=3750milliwatt load and the second one for a 550*15=8250milliwatt load (for devices rated at 15v). The smaller one must belong to the preamp and the bigger one to the turntable. (considering this link) Connecting the wrong power supply means it will not be able to supply enough current and most probably overheat and fail with no damage to the device it is connected to.

1p2r3k4t
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