thank you for the answer. It looks so that not so much experiences with the japanease version exists.
My next idea is to exchange the complete firmware. My first step was now to read out the original firmware with the "ebook_msc.exe" and option "fulldmp". This works great except the Block16. I copied this block with the "get" option manually. This block looks like the user acesseble internal space.
The next step is to find out if the blocksize is the same in japanease and international version. To check this I need somebody who reads out an international PRS650. Who can do this ?
I attached the blocksize of J-PRS650 for compare.
If both version has the same blocksize it must me possible to convert a J-PRS650 to PRS650. Or not ? How is the risk to brick the device ?
Does anyone know what kind of data the different Blocks contains ?