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Re: [TowerTalk] Prosistel PST61 Control Box problem

Subject: Re: [TowerTalk] Prosistel PST61 Control Box problem
From: "Roger (K8RI) on TT" <>
Date: Sun, 14 Aug 2016 23:04:07 -0400
List-post: <">>
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 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)


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.




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