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Old 03-08-2012, 03:35 AM   #1
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AC adapter question (polarity)


Hey, so I have a keyboard I want to power via an AC adapter, so medium story short, the back of the keyboard has the Centre positive symbol (http://en.wikipedia.org/wiki/File:Centre-positive.svg), and the adapter has the Centre negative symbol (http://en.wikipedia.org/wiki/File:Centre-negative.svg) (although the centre 'C' is reversed, so the open centre dot goes directly to the + on the left.). See diagram.

Should the polarity symbols match? All other specs are as per the product page/manual (http://www.akaipro.com/mp6-1): 6V DC 1A. Although no mention of the mA's on the adapter.

Oh, and the nib (ending bit of the adapter is yellow, and not black as per the product page linked above).

I sent a message to the manufacturer, but did not include the polarity part. The adapter was from an authorised dealer.

Thanks!


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Last edited by bugmenot; 03-08-2012 at 04:04 AM.
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Old 03-08-2012, 05:42 AM   #2
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AC adapter question (polarity)


Your diagram shows the center pole as positive in both situations. Just drawn different. 1A = 1000mA. Reverse polarity will not work in that device and may burn even burn it up.

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Old 03-08-2012, 12:49 PM   #3
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AC adapter question (polarity)


Okay, thanks. It dawned on me the centre tip may be positive, just odd they drew the diagram wrong, err upside down.

On the product page it shows 6VDC @ 500mA's. But on the back of the keyboard it has the 6V DC 1A as I mentioned. Does that mean the adapter cannot exceed 1A?

Last edited by bugmenot; 03-08-2012 at 02:36 PM.
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Old 03-08-2012, 02:58 PM   #4
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AC adapter question (polarity)


A 6v, 1A adaptor will probably read 7v with no load which means it's internal resistance is (7-6)v/1A = 1 ohm which means it will supply 2A at 7v-2A(1 ohm)= 5v with a shortened adaptor lifetime.

Some DVMs have a diode test which you can likely use to test proper polarity for your keyboard.

Last edited by Yoyizit; 03-08-2012 at 03:02 PM.
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Old 03-08-2012, 04:29 PM   #5
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AC adapter question (polarity)


I don't own a DVM.

Didn't really get the first part, I am far from an expert!

So in regards to the mA, it seems okay to use? (Adapter shown on manufacturer website shows 500mA, this one is 1A.)
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Old 03-08-2012, 05:24 PM   #6
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AC adapter question (polarity)


Quote:
Originally Posted by bugmenot View Post
Adapter shown on manufacturer website shows 500mA, this one is 1A
Yes.
You ought to buy a meter, it'll pay for itself pretty quickly.
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Old 03-09-2012, 02:27 AM   #7
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AC adapter question (polarity)


Thanks for the help!

So out of curiousity, since the one they link to is 500mA, and it asks for 1A, isn't that bad, as the adapter may overheat?

And lastly, some devices can use adapters with reverse polarity?
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Old 03-09-2012, 08:07 AM   #8
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AC adapter question (polarity)


As long as your equipment does not draw more than 1A the power pack will operate within its design range. Many semiconductor devices will not operate right under reverse polarity. Some may even cook.
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Old 03-09-2012, 11:29 AM   #9
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AC adapter question (polarity)


I'm not sure anymore what to do.
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Old 03-09-2012, 02:32 PM   #10
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AC adapter question (polarity)


Your power pack is 500ma and your keyboard needs 1 amp or 1000ma. That's twice what your power pack can supply. You need a bigger power pack. Just go to Wal Mart and get a universal power pack with changeable tips. And pick up a cheap meter while your there. Set the voltage to 6V with the center positive. That would be red lead of tester on center showing 6V and not -6V. Hope this helps.
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Old 03-09-2012, 03:06 PM   #11
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AC adapter question (polarity)


@shumakerscott My adapter is 1A, but the one recommended (linked) from the product page on the manufacturer's website is a 500mA one. Which I found odd after realising it indeed wouldn't supply enough power.
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Old 03-09-2012, 03:28 PM   #12
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AC adapter question (polarity)


Quote:
Originally Posted by bugmenot View Post
@shumakerscott My adapter is 1A, but the one recommended (linked) from the product page on the manufacturer's website is a 500mA one. Which I found odd after realising it indeed wouldn't supply enough power.
Ok, If you have a 1 Amp adapter, 1000ma and your keyboard needs 500ma then you are good to go . Make sure the center is positive with 6 volts and make music. Your adapter must meet the minimum requirement on amp's but can be larger not smaller. The volts must be the same. dorf dude...
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Old 03-09-2012, 05:25 PM   #13
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AC adapter question (polarity)


Thanks, yeah, I am pretty certain I am good to go, just wanted to be 100% sure.

The first post has a diagram I made, and for some reason, I'd say since it was made in China, but probably a lot are made there, but the polarity diagram was upside down.

On a sidenote, the keyboard shows 6V DC 1A, it was the adapter they linked that show 500mA, hence the puzzlement once I realised that. Maybe I'll follow up and ask out of curiousity...
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Old 03-09-2012, 05:34 PM   #14
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AC adapter question (polarity)


If the product reccommends a 1000mA supply or 1 A,
Then thats what you should use !
It will probably work with a smaller 500mA supply,
cause it wont pull 1000mA continuously,
only very occassionally.
So under some circumstances you may have problems,
And the life of the smaller supply would be shortened.
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Old 03-09-2012, 07:55 PM   #15
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AC adapter question (polarity)


Quote:
Originally Posted by bugmenot View Post
Okay, thanks. It dawned on me the centre tip may be positive, just odd they drew the diagram wrong, err upside down.

On the product page it shows 6VDC @ 500mA's. But on the back of the keyboard it has the 6V DC 1A as I mentioned. Does that mean the adapter cannot exceed 1A?
It's not drawn upside down....you are looking at it upside down. (those symbols, like many others don't have a right side up)

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