Re: Clean and Lubricate Pots in Tek 475


 

You are describing the "A & B" (Allen Bradly) pots. I just got through going completely through my 475 after years of putting up with attenuator "leaf springs" not making good contact and the vertical and intensity pot problems you are seeing in you father's 475. I removed the vertical board preamp board and unsoldered these A&B pots from the PC board. I then removed the 4 screws and completely took these vertical position pots apart. I put a little Deoxid into them and tried to find the problem with the stiffness and the "springback" of these pots with little success. For some reason I could not locate why they turn ok when apart BUT are stiff when assembled. Fortunately I had picked up a "parts" 475 some years ago for fixing up my 475. The parts 475 had Bournes installed in this unit in all of the areas of vertical position, brightness, horizontal position, astigmatism, focus and so on. So I bit the bullet and did the work necessary to change the Bournes pots into my 475. This requires removing the necessary PC boards in some cases and is a pain in the ass. I see a seller on the bay that is selling the 311-1397-00 vertical pots that are brand new. I would suggest strongly that you buy these and save yourself a lot of grief in the long run. He also has the horizontal position pot and others for this scope. Now my 475 controls work just like they did from the factory and intended. I don't know why the A&B pots fail years later. The A&B pots seem to be used in the early units and then the Bournes in the later units. Maybe because A&B went out of business?
But after cleaning the gold contacts in the attenuators and generally cleaning up this area I am now very happy. Do the work and you will be happy with the results.
Bill

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