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Prosistel rotator failure

Following some strange behaviour of my prosistel rotator I luffed my antenna over to check to see what was going on.

This is what I found:

The picture was taken as i was taking the bolts out of the bottom flange, thus the 'empty' mounting hole on the left.

The rotator is supposed to be for large antenna systems, but it appears the rotator part of the unit is held on to it's bottom flange by what appears to be four 1/4 inch counter sunk machine screws. The four holes can be seen on top of the flange. Three of these screws had sheared and the remaining screw had started to badly wear the remaining hole.

March 2011

I stripped the rotator and had the rotator body welded to the bottom casting, like so:


The internals of the rotator were fine and wear free. As such I rebuilt it and filled the body with suitable gear oil.

I refitted the rotator to the tower in May of 2011.

Note: If you contact the company in Italy asking for information, or advice on how to repair your unit, what you receive will be very limited, and not much use at all, bar the fact they will offer to repair the unit for you if you return it to them.  It is my opinion that the reason for this is because not all rotators are the same. You may have a PST61, but what version? and that's where the company falls down as even they can't tell you. A second note is that out of 6 different prosistel rotators here, there have been 5 failures of the control box. Each time it has been found that the main transformer has failed. I suspect that the design rating of the transformer is on the limits of what it can do, and eventually fails. I have replaced transformers as and when they have failed with ones rated at +50%. These modified units have been OK since then change.

repair details of an old style PST61 by: Roger (K8RI)