Those in need of a new replacement drive for the Hall mounts sold by Astro optical can buy one from McLennan Servo Supplies. I did a lot of digging and found these guys a while back but only visited them earlier this year. The original drives were supplied by Phillips and were either made by Mclennan's or they supplied most of it. The original is no longer available but supersedes to P531 SP111 G19 L01, if you don't have the original you will need to supply your own worm gear and phase shift capacitor (and wire it, diagram was supplied). These are not cheap and nasty but a quality unit , priced accordingly. They usually have a 100 GBP minimum, so buy 2 or contact them and ask nicely.
I don't have any dead Sampson drives but they can make anything needed on site if you can supply the detail (photo and details on gearing, output shaft dia, part number on drive gearbox and motor etc) . I found then extremely helpful and despite dropping in unannounced they built 2 drives for me and had them delivered to me in London within 4 days (everything is assembled to order no stock of complete drives is held).
http://www.mclennan.co.uk/
