[TowerTalk] Prosistel PST61 Control Box problem

[Roger (K8RI) on TT]

He is referring to the PST61, not the D version. (old or new versions?  
New uses a DC motor) They look the same and I believe have the same 
internal parts, but with a different motor.

For the internal parts of the PST61 (old style) see 
http://www.rogerhalstead.com/Gears.htm This has a lot of photos and is a 
large page. I'd not recommend it for a dial-up connection. It does cover 
almost everything in there.
I believe the new ones are similar.

The body of mine is held onto the mount with 4, (I believe 6mm ) bolts,  
not machine screws. HOWEVER they are inadequate for the PST61s full 
ratings, let alone the D models ratings.  I've never seen them sheared 
in a PST61, but rather the threaded holes failed. This is cast Aluminum 
which is rather soft.   The caps on those bolts are shown in photo 32 at 
the end of the page, but I have no photos of the actual bolts. The cover 
for the 10T pot is screwed to those.

*NOTE: *When replacing this "10 turn" pot, make sure to determine the 
wiper position before, or when removing the failed pot. Measuring the 
resistance of a failed pot is not reliable, so with the rotator and one 
end of it's travel, or a known position, you can count the turns of the 
pot CW, or CCW to the end. Be sure to write it down.

On mine the position of the wiper was near the middle of the 10 turns.

They have addressed the original problem of water in the top seals 
causing the output shaft to rust (photo 4) on later models. How well 
this works? I don't know, but it looks good.  The early models with the 
AC motor had the top seals recessed with a raised ring (abt 1/4") around 
it. (photo 18)  The rusted shaft not only abraded the seals, but formed 
an additional path for water entry. Water being more dense than gear 
lube will sink to the bottom carrying rust along with it. destroying the 
bottom bearing and rusting the bottom shaft. Water will quickly cause 
the top bearing to fail.(Photo 2) Note the keyway in the output shaft 
(photo 13)

73

Roger (K8RI)

> The idea of the Prosistel is a good one, it’s just built to a price, and in some places it shows.
>
> The PST61 of mine that failed, was due the FOUR tiny metal machine screws that hold the rotator onto the bottom casting. There’s no interlocking castellation’s or anything like that, your large antenna relies on those four small screws, and once they fail, (and they will if you have a large antenna) your rotator will need a repair and more than likely modification at the same time.
>
>   
>
> 73
>
> Andy
>
>   <http://gd0tep.com> http://gd0tep.com
>

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