I once lost the Korg PA50's power adapter somewhere in my store and was desperate to find another that would work. I used a Yamaha PA5 adapter and although it worked, it did cause the Korg PA50 to produce a low volume hum. I used it for a couple of weeks until I found the Korg AC and the hum was gone. I would be careful!
I'm also surprised that the PA-300 is an option in your country because the keyboard can't work without the adapter. Here in the USA, if a keyboard can run on batteries, the AC adapter is usually an option, but in the case of the PSR3000, it won't work on batteries so they have to give you the AC adapter.
I have had customers through out the adapter with the box because they didn't realize the adapter is packaged in it's own brown box at the bottom of the PSR3000 box.
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George Kaye
Kaye's Music Scene
Reseda, California
818-881-5566
www.kayesmusicscene.com