I tried ddrescue & testdisk and here are the errors:
# ddrescue /dev/ad7 testdump sdb.log
Press Ctrl-C to interrupt
Initial status (read from logfile)
rescued: 0 B, errsize: 0 B, errors: 0
Current status
rescued: 0 B, errsize: 0 B, current rate: 0 B/s
ipos: 0 B, errors: 0, average rate: 0 B/s
opos: 0 B
# testdisk /log /dev/ad7
TestDisk 6.9, Data Recovery Utility, February 2008
Christophe GRENIER <grenier@cgsecurity.org>
http://www.cgsecurity.org
Unable to open file or device /dev/ad7