SHORT

Thanks, I also found a service manual for MZNH700/MZNHF800 at minidisc.org (yes, there is only one manual for these two rather similar toys)

Bad news is: I accendently erase the patch and my MZ-NHF800 was dead as a rock too. I try a lot of adjusting... after hours of playing with those small buttons and the big dial (compare to my mz-r900 it's really big), it still show me noPach. Just before I want to give up, or when I decided to give up. I am at the deadly "NV 921 PatVer" menu. I press the pause key again and thinking whether I should use fedex or UPS to send it back.....While the small disk is running on the little screen, I think what the hack, then I just pull out the USB line.....At that moment, there is neither bettery nor AC. So, essentially, I remove all the power while the unit is trying to write something into somethere.... The good news is My MD MYSTERIOUSLY REVIVED!!! Immediately after that!! I am able to play, My computer can see this little "Removable Disk" drive and read/write files on a 80min MD disk in hi-md mode... Currently my one and the only 1GB disk is not around me, so I can not test it. I do go back and check again, the "NV 921 PatVer" it stil showing me noPach.. Why don't you give it a try. and see if this work for you. BTW, the major change I have down while playing with the service mode includes NV 112, NV 113, NV924, and of cause NV921. Good luck! and wish AOIX can give some good news back