A recnt Western Digital 500GB disk was spinning, but not recognised by a PC with USB connector. The next test I always try is with Ace Laboratories PC-3000 which is designed to test abd refirm driver firmware. At first this would not recognise the disk under general routines, but when the WD funtion tests were tried some response was found. It was not enough to recognise which family the drive belonged too, and so this was a case at looking at all the PCB layouts and matching a photo. Eventually the short list was 4 possible drive types, of which Tornado 2D was found to work.
The PC-3000 did a series of tests, and end of which it was possible to view a sector.
I did not know how long this reading would last so I started a Read to file and this moved very slowly, but positively. After a few hours the reading sped up to an acceptable rate. Over night over 200GB was imaged, but then the reading had gone painfully slow. I stopped the read and confirmed that other areas of the disk could be read without significant delays. The problem with PC-3000 is that it is not very good at reading sections of disks in an easily managed way.
The next stage was to carefully disconnect the SATA cable from PC-3000 and connect a PC (USB) SATA connector, without turning the drive power off. To my delight, the PC would read the disk anda process of incremental imaging was continued. I started with the final 200GB or so of the disk, and slowly worked back to the area that caused so many problems. When I had managed to image probably over 99% of the I decided the return rate was probably too small to consder worth continuing. The image produced a very healthy recovery of the disk, thanks both the PC-3000 and Incremental Imaging.