I had a WD2500 Hard Drive that was not working, no spin up or anything. It seemed that the board was not working, but there was no signs of failure.
Fortunately, I found another WD2500 board which was working.
A simple board swap did not work, the heads started chattering when plugged in.
To really fix it, it is necessary to remove a 8 pin rom chip on the “broken” board and solder it to a “good” donor board. If you cannot do this, find someone who can or you will get nowhere.
Once this was done, the hard drive started without a problem, the data was dragged off ASAP.