In operation both motors run in opposite directions and movement direction is selected by applying the appropriate clutch. A tachometer feedback closes the control loop for rate control with both resolvers and quadrature encoders providing position feedback. One spring-set brake is used for each axis. The clearances required between the pinion and the ring gear added to general gearbox backlash generates some noticable backlash errors in azimuth but under normal operation they do not affect operations. The bearings in the clutch unit had failed and one shaft had to be machined.
All gearboxes appear to be in good shape.
The dish rotates in elevation on four 30 inch Timken roller bearings which are in good shape. The screws are covered with fabric boots which are in very poor shape, providing very little protection. The boots need to be replaced and the screws and nuts should be refurbished by cutting new groves and installing larger balls. The covers over the lower parts of the screw jacks can be seen in most photos of the dish, they are the long rods shown sticking down from the back of the dish. The error can be accommodated in software.