I need help to fix the timing on my Singer?

I have a Singer Electronic Control numbered 57820 C - no other identifying number, sorry. My problem is that the top and bottom threads are not connecting to form stitches as the hook is not picking up the top thread from the needle and looping it around the bobbin thread. Assuming this to be a timing issue, I have been playing with the positioning of the hook in relation to the needle but am not having too much luck. To give me a better chance of getting it right, could you please tell me whether the needle should be almost as far down as it can go, as far down as it can go or slightly on the rise back up at the moment the hook makes contact with the thread. Also, if you don't think that the timing is the issue could you give me some ideas of what it might be.
Thanks,