Instruction: Answer the given question using the supporting document.

Input:
Question: Center pin positive or negative?
Document: I got this for my Casio keyboard. in the move, my old power supply went missing, so I went to amazon for a cheap replacement. First off, if you can't solder and you need the center pin to be negative, don't buy this. this is backwards of the industry center of grounded pin, positive shield.
I needed a 9 volt DC adapter with center pin negative so I thought this would not be suitable until I saw the Philips screw holding the unit together in a previous picture review. I ordered the adapter and for $5.82 I got it with free shipping as I'm Prime.When it arrived I opened up the adapter and de-soldered the positive and negative terminals and then swapped and re-soldered them, put the adapter together and plugged it in.
I use this for a guitar effects pedal because it is a lot cheaper than most pedal adapters. The only thing is you have to have a little cable to switch the center and the outer connection to make the positive on the outside. I happened to have one laying around so I am using that. if you buy the visual sound one spot adapter kit it will come with two of them.
I ordered the 9 Volt DC adapter for my keyboard and got exactly what I needed. I found that for my specific application I had to switch the leads (positive/negative) - the adapter came as positive inside, negative around. I was aware I might have to switch the leads.Shipped fast, works well.
ATENTION: CHECK POLARITY BEFORE USE IN ANY CASE!!! !9 Volt Direct Current, 1 Ampere max(that's ok), BUT, if you want it for a CASIO CTK KEYBOARDS you must change wires!!!! PROCEDURE: CUT THE CABLE in the midle, INVERT WIRES, RED TO BLACK, BLACK TO RED!!! Then check voltage, must be: Negative inside, Positive Outside !!!!.
would have gave him a 5 Star, but it didn't fit my box. Pin hole was to small. Not worth returning. But product was good.&#34;They said they would refund my money. Haven't seen that yet.
(Written by Marcus Brooks, Shea's OM)After reading some of the negative reviews, I clicked More Buying Options and paid a little more for a US seller with a top rating. This seems to have paid off.The supply I received appears to be well built and works fine. I used it to replace the burnt-out 500mA 9Vdc supply on an LED lamp, which it powers easily without heating up at all.
works like a charm...bought it to replace my broken adapter for my ipod radio...and it was music to my ears..just the right fit..would buy another if it got broken
works fine so far, I used for some weeks and still working. I will check again  in a few weeks
wont work
Answer: Center pin is positive