Good news, I managed to rescue all my data (except a few blocks) by reading many threads in this forum and experimenting a lot. Thank you very much for all the information here.
LarrySabo wrote:
Given their history, I don't know why anyone would want to resurrect a failing DM drive, especially as there is no data recovery required. Just bin it and vow not to buy another Seagate, is my advice.
It was an interesting experience, I have learned a lot and finally got all my data back, so was totally worth it. However I will never buy a Seagate device again − this was clearly a software related issue and it was a way too hard to find some good information about this particular devices. Especially if you have no specific data recovery software or hardware.
labtech wrote:
P.S. Don't try things off the internet without understanding clearly what is going on. Educate yourself first before issuing commands in the terminal.
This was a really good advice, however at the time of your reply I had already messed up my device by issuing some commands (I am a little bit risky sometimes). In retrospect I think clearing all the SMART data should have been enough, but I also regenerated the translator with the wrong command which does not take the NRG list into account. So I ended up with the partial access error. I had a backup (terminal dump) of the old NRG list but I was unable to find out how to add entries manually. I finally cleared the NRG list with
i40,1,22 and regenerated the translator again. After this I was able to access the full device but I got some bad sector errors because all the previous mappings had gone (if I understand this correctly). But it worked and all my "nice to have them back"-files are not damaged.
Initially I was unable to send commands to the drive because the voltage was too low. Although the device sends using a 2V logic level voltage it does not recognize any input using this voltage. I simply used the direct 5V output of the USB to Serial converter and it worked.