Mains adapter for midi controller

[aural roberts]

Normally I power my Evolution MK-449C midi controller via USB but I now want to use it away from the PC and so need to use a mains adapter. The manual states that such an adapter should be 9 volt, 300 ma - I already have a 9 volt adapter but the amperage is 800 ma. Would I damage the keyboard by using this adapter ?

[whyterabbyt]

800mA is the maximum rating the adaptor can deliver, so its capable of handling your 300mA keyboard, yes. Just make sure you've got the polarity of the plug into thethat goes into the keyboard right.

[aural roberts]

Thanks, the manual says the polarity should be centre positive. My adapter has a switch that lets you select the polarity - I'm guessing that the setting that shows a "+" sign at the tip is centre positive. If I'm wrong will it just not work or could this cause damage ?

[noizetronic]

Reversing polarity can cause damage. I would want to be sure about it before plugging. Use a multimeter, if at hand.

[whyterabbyt]

Thanks, the manual says the polarity should be centre positive. My adapter has a switch that lets you select the polarity - I'm guessing that the setting that shows a "+" sign at the tip is centre positive. If I'm wrong will it just not work or could this cause damage ?

Generally, the '+' means tip-positive. But what noizetronic says is correct; if it doesnt explicitly say that, test it, because it can cause damage.

[hersoot]

Normally I power my Evolution MK-449C midi controller via USB but I now want to use it away from the PC and so need to use a mains adapter.

I also have an MK-449c. At a local electronics store I bought an inexpensive (less than $2) battery "holder" for 6 AA batteries to which I connected a wire and plug. The batteries power the controller forever; well, a long time.

[noizetronic]

Maybe you have some other device that's cheap and suitable for testing. It should have something like this on its case:

Code: Select all

    |--
- --| o-- +
    |--

Check for proper voltage as well, test quickly. If it was the wrong direction then at least you'll still have your midi controller.

[C00kie]

Thanks, the manual says the polarity should be centre positive. My adapter has a switch that lets you select the polarity - I'm guessing that the setting that shows a "+" sign at the tip is centre positive. If I'm wrong will it just not work or could this cause damage ?

Your guess is right. Usually it's shown like this:

I've never had any damage caused by reversed polarity power, although it happened to me numerous times. Just don't push it, and disconnect it immediately if the unit won't power up. If you don't want to run any risk at all, you should check the polarity with a volt meter.