Pulley Creep

Discussion in 'Tuners' started by boreas, Nov 1, 2017.

  1. boreas

    boreas AK Subscriber Subscriber

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    That might work but the hole in the spur gear is only about 2.5mm in diameter and the gear itself is pot metal so there's a posswibility that the gear might break while cutting the ditch in it.

    John
     
  2. Oerets

    Oerets AK Subscriber Subscriber

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    I did a Sansui tuner awhile back with that same setup. Don't remember the movement your describing. It's problem was not full movement. Only half the dial. Somehow it was off by 180* on the keying. Have you tried moving the drum in more when the gear shaft is out? Tighten it down and see if it will stay then. You do not want to disassemble the gear housing at all! A RPITA!!!!!!


    Barney
     
  3. Pio1980

    Pio1980 AK Member Subscriber

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    This is all too common with these VCs and a major pain in the ass.
     
  4. boreas

    boreas AK Subscriber Subscriber

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    Hey, Barney -

    Yes, I tried moving the drum in and out. Neither direction solved the problem. I think the only remedy is to somehow bond the spur gear to the shaft.

    John
     
  5. boreas

    boreas AK Subscriber Subscriber

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    Yeah, Steve, tell me about it!

    John
     
  6. Oerets

    Oerets AK Subscriber Subscriber

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    Is there a hole in the end for a screw to thread into the drum thus shaft?


    Barney
     
  7. Pio1980

    Pio1980 AK Member Subscriber

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    No.
     
  8. boreas

    boreas AK Subscriber Subscriber

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    It's not the drum moving on the shaft, Barney. The shaft and the drum together are backing out of the tuning cap. When the shaft has backed out far enough so that it's free of the pilot bushing, the shaft tilts sideways because of the tension from the cord and that pulls the spur gear so that its teeth don;t engage the teeth on the anti backlash gear and the cap she's a no spin.

    John
     
  9. Oerets

    Oerets AK Subscriber Subscriber

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    Hope these pictures can help. Didn't really want to be opening a unit this late or after a few adult beverages. Had to relax hit a doe at dusk on the interstate.

    But that's another story for another day.

    Anyway here is the Sansui with the same setup.


    Barney
     

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  10. boreas

    boreas AK Subscriber Subscriber

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    Thanks, Barney. That looks a little different from the one in this Onkyo, more open and accessible. Plus it has a double drum, which makes no difference in this situation.

    Any venison on the menu? :D

    Hope the car's not too bad.

    John
     
  11. Oerets

    Oerets AK Subscriber Subscriber

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    Not this time. Hope she made it home last night. Was able to slow down considerably before the Doe' left shoulder hit my Ram's right headlight. Stopped by a carwash and under their lights the only real damage seems to be the headlight. Got lucky it evens still works just cracked!

    I will try and take better pictures in a bit. Getting better details. I had to take the gears assembly apart on the Sansui. You want to avoid this at all costs.


    Barney
     
  12. chazix

    chazix AK Subscriber Subscriber

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    Maybe I'm too simple-minded and/or pragmatic, but my approach to these cases is to add some cobbled-up structure that contacts the outer end of the shaft (or center of the drum). The added structure acts to keep the shaft from backing out of the VC. The added friction, especially since it acts at the rotational center, is negligible. The VC is typically near the perimeter of the unit's chassis, and it's usually possible to find a way to fasten the structure to the chassis. Doesn't need a lot of mechanical robustness - it's not like there is much force behind the backing-out tendency.

    I guess I'll mention one of my favorite materials for fabricating the structure - it's the wire used to close your average paper carton of rice or what-not from an Asian take-out order. The wire is plenty strong enough to counter the backing-out, but it's easy to bend into whatever shape is helpful for fastening to the chassis. I usually make a kink in the wire, such that the point of the kink is what makes contact with the tuning shaft/drum.

    Cheers,

    chazix
     
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  13. Oerets

    Oerets AK Subscriber Subscriber

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    Here are a few shots from a Luxman under the knife and just finished up. It has a setup more like yours is. Hope the new pictures help some.


    Barney
     

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  14. Pio1980

    Pio1980 AK Member Subscriber

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    This provisional outer end limit stop approach is pretty much the best and only fix I've imagined for this all too common problem. Something sufficiently rigid to prevent the shaft assembly from drifting out of mesh.
     
  15. Oerets

    Oerets AK Subscriber Subscriber

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    Here is another one...

    It looks to me the gear is all the way in, no gap.


    Barney
     

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  16. boreas

    boreas AK Subscriber Subscriber

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    Thanks, Barney. That looks like the exact same setup.

    John
     
  17. boreas

    boreas AK Subscriber Subscriber

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    Thanks! You guys are brilliant!

    The thing that struck me first and almost made me discount your suggestions was the fact that a wire would have to deal with, and potentially get hung up in, the slot for the cord, cord itself or the tension spring. You could avoid most of these pitfalls by having the wire ride on the edge of the drum but slot is still a problem and a wire might slip off the edge of the drum and lose contact with it.

    But what about something wide enough to glide over the slot unperturbed and deep enough to accommodate some vertical movement without slipping off the drum? So I started rummaging in my junk bin. Here's what I came up with.

    Dial Pulley 003.JPG

    Not exactly this one. A smaller one that I cut down to fit. It ended up looking like this.

    Dial Pulley 001.JPG

    Dial Pulley 002.JPG

    It seems to exert enough pressure on the drum to keep the shaft in place and, at the same time, is largely unstressed so probably won't fatigue and break or deflect further.

    Best of all, the fix took all of 5 minutes, a far cry from the hours I put in trying to glue the shaft to the spur gear.

    So, I think it's fixed! At least I'm prepared to put the tuner in service and see what happens.

    Thanks to all who helped guide me through this problem, especially the outside-the-box thinkers among you.

    Cheers!
    John
     
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  18. Oerets

    Oerets AK Subscriber Subscriber

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    Lookin good!



    Barney
     
  19. Dave_1962

    Dave_1962 Lunatic Member

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    Clever! Here's hoping it performs as you wish_:thumbsup:
     
  20. boreas

    boreas AK Subscriber Subscriber

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    Thanks. It does, as far as I'm able to tell. Lots of dial spinning and no movement at all in the shaft. The only thing that might alter that is if the plastic cable clip fatigues/breaks.

    John
     

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