Another turntable alignment mystery

It was going great! I was confidently soldering socket after socket onto the lazy Susan, using a temporary pin to align them with the fixed tube. It was going so well, in fact, that I thought I might get on to soldering up the electrical connections tonight.

Well, not so fast. When I had soldered all eight sockets into place, I turned the baseboard over and tested them. They should work, right? I mean, I had clamped the turntable in alignment, and soldered the sockets with the pin driven into them. Then releasing the clamp leaves the turntable aligned. So far so good. But then I tested some other tracks, and then came back, and driving the pin into the socket doesn’t align the turntable.

Now, if it were off by a smidge, I could understand. But it’s off by a lot! So there is clearly something here that is beyond my comprehension. The misalignment seems to be related with knocking one of the sockets against my temporary clamp (a screw), which I have done several times. It really seems like something is moving, and I guess I shall have to figure out what it is.


2 thoughts on “Another turntable alignment mystery

  1. Overnight, I came to the theory that what’s happening is the turntable is shifting relative to the platter. It is held on only with screws through PC board. The holes are likely wearing, and any shift there is going to be linearly amplified at the edge of the turntable.

    Indeed, it requires scary precision to work, and I should have thought of this before (if I were an engineer like Mark, instead of a bodger, I would have done this calculation before). Because the turntable is about 100 mm in radius and the screws are about 5 mm from the centre, a shift of 0.05 mm yields a misalignment of 1mm at the edge where it matters.

    It seems like I’m going to have to pull the lazy susan off and build a little socket to squeeze the turntable pedestal. Fun!

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