Sonora Auto Stop Repaired

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audiophile102
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Sonora Auto Stop Repaired

Post by audiophile102 »

The auto stop on my Sonora Elite is not functioning as it should and I could use some help from the fine folks on this forum. I made a short video showing the auto stop in action and I posted it on my You Tube channel. If you are mechanically inclined, please take a look at the video and let me know if you have a solution. Thanks.

UPDATE: Roger Merenkov examined the auto-stop and found a solution. Check out the video I posted on my You Tube Channel if you are interested. https://youtu.be/ctRyDko2NMI
Last edited by audiophile102 on Sat Apr 15, 2023 5:10 pm, edited 1 time in total.
"You can't take the phonographs nor the money with you, but the contentment the phonographs bring may well make your life better, and happier lives make the world a better place."

pallophotophone
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Re: Help Request - Sonora Auto Stop

Post by pallophotophone »

Hi !

Just some observations because I've never found one of these. But mechanicals are still mechanicals.

1- The small spring you mention I think is a torsion clutch that is designed to allow slip so that if the stop mechanism jams, the gearing would not be damaged or the turntable to stall.
2- Since the long lever continues to move, the problem lies with the breaking mechanism that the lever engages. Your video doesn't show much in that department. But I'm sure that is where the problem is.
Study the breaking mechanism and the remedy will become very obvious ! You should be able to move the long lever without the motor running and see what is or is not making mechanical contact as it should.

Good Luck - I don't think you will need it !!

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audiophile102
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Re: Help Request - Sonora Auto Stop

Post by audiophile102 »

Thanks for your analysis. The auto brake works intermittently which is puzzling. When it refuses to trip the brake, I apply very gentle pressure to the auto brake lever and it instantly trips the brake. I still suspect the torsion clutch is the problem, but the parts are so small and my ideas so vague I'm reluctant to monkey around with it. I tried buffing the part of the long lever and the bottom of the brake lever in order to minimize any friction. I used very fine sandpaper until the parts shined, but it didn't seem to help. I don't know if I will ever figure it out, but one suggestion I received involved using a small amount of super glue directly on the torsion clutch spring. I don't like the idea so I will take my time and study the problem further. I can move the long lever without the motor running and it's working just fine. Again, the auto brake does work intermittently so it's all the more puzzling. :?
"You can't take the phonographs nor the money with you, but the contentment the phonographs bring may well make your life better, and happier lives make the world a better place."

pallophotophone
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Re: Help Request - Sonora Auto Stop

Post by pallophotophone »

I'd NEVER use superglue, even the most miniscule amount on any clutching mechanism. If it jams the damage it could cause could be extensive ! The amount of torque generated by the turntable drive is very high
It's hard to tell from pictures, but my bet is on something sticky in the break assembly itself. Your finger pressure on the lever is just enough to counter act that stickiness.

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audiophile102
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Re: Help Request - Sonora Auto Stop

Post by audiophile102 »

Here are some close-up shots of the torsion clutch. The parts are tiny and the idea of taking it apart has me intimidated. Until I find a definitive answer, I will continue to manually push the stop lever. I can see why Sonora abandoned this braking mechanism the following year. Rube Goldberg would have liked it. https://youtu.be/40AO2RdEixs
04  torsion clutch.JPG
03  torsion clutch.JPG
02  torsion clutch.JPG
01  torsion clutch.JPG
"You can't take the phonographs nor the money with you, but the contentment the phonographs bring may well make your life better, and happier lives make the world a better place."

pallophotophone
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Re: Help Request - Sonora Auto Stop

Post by pallophotophone »

You'd have to push down on the spring and then pull the retaining pin. I doubt you'd gain anything from it. But you might soak the entire assembly in parts cleaner for some time just in case excess oil might have gotten into the spring/shaft area that shouldn't be there. But it probably should have a very tiny amount of oil in it so it can slip when it needs to such as when the lever gets reset.

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audiophile102
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Re: Help Request - Sonora Auto Stop

Post by audiophile102 »

pallophotophone wrote: Sat Apr 01, 2023 1:30 pm You'd have to push down on the spring and then pull the retaining pin. I doubt you'd gain anything from it. But you might soak the entire assembly in parts cleaner for some time just in case excess oil might have gotten into the spring/shaft area that shouldn't be there. But it probably should have a very tiny amount of oil in it so it can slip when it needs to such as when the lever gets reset.
Thanks for your advice. I tried removing any accumulated oil by washing it with an old toothbrush, detergent and water. I carefully dried it and put it back together. It had no benefit. I didn't add a tiny amount of oil, but I will. I have examined the switch carefully and it works effortlessly. At this point my best guess is that the design was flawed when drawn up in 1913. Getting it to work again might only be temporary. Still, I like a challenge and maybe a solution will present itself. I'm in no rush and I am patient.
"You can't take the phonographs nor the money with you, but the contentment the phonographs bring may well make your life better, and happier lives make the world a better place."

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