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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 25th Jan 2020, 4:26 pm   #1
Paul Mathew
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Default DUAL technical info needed

Anyone have any technical info on this DUAL motorized turntable?
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Old 25th Jan 2020, 5:30 pm   #2
Audio1950
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Default Re: DUAL technical info needed

Could you post pictures of the motor, please?
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Old 26th Jan 2020, 10:25 am   #3
Paul Mathew
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Default Re: DUAL technical info needed

I thought that should have been included! Thanks for the interest.
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Old 26th Jan 2020, 11:59 am   #4
Werner
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Default Re: DUAL technical info needed

Could it be that one: https://www.radiomuseum.org/r/dual_d...it_undy_t.html ?

Greetings,

Werner
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Old 26th Jan 2020, 1:31 pm   #5
Paul Mathew
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Default Re: DUAL technical info needed

Danke, das sieht identisch aus! Is it a good idea to bring the motor up to voltage using a variac? Can this do any damage?
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Old 26th Jan 2020, 1:41 pm   #6
Audio1950
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Default Re: DUAL technical info needed

I have three identical motors in acoustic gramophones, but with spring mechanisms attached, so that the motor can be either wound up, or plugged into an electrical socket.
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Old 26th Jan 2020, 3:22 pm   #7
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Default Re: DUAL technical info needed

By coincidence I picked up the attached motor assembly at my local car boot yesterday.
It was in a box of junk that would otherwise be skipped eventually, I had to rescue it (honest).
I assume it is also from an acoustic gramophone.

How does the governor work? is it purely mechanical or does it operate a switch when overspeed?

Peter
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Last edited by Electronpusher0; 26th Jan 2020 at 3:23 pm. Reason: typo
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Old 26th Jan 2020, 4:08 pm   #8
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Default Re: DUAL technical info needed

Purely mechanical, the disk bit rubs on the felt bit when up to speed slowing it down. Shunt motors like that don't mind too much when loaded and they slow down gracefully.
 
Old 26th Jan 2020, 5:21 pm   #9
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Default Re: DUAL technical info needed

Thanks, Any idea what voltage the motor runs at? unfortunately the voltage on the motor rating plate is blank.
I thought possibly it was 220V being French?

Peter
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Old 26th Jan 2020, 6:07 pm   #10
Michael Maurice
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Default Re: DUAL technical info needed

I'd run it up on a variac if you can, start at 110-120V and feel the temperature of the motor, then crank it up to 150V, then 200, then perhaps 220-240. All the time keep an eye on the temperature of the motor.
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Old 26th Jan 2020, 6:26 pm   #11
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Default Re: DUAL technical info needed

The unit in the Radio Museum link has a voltage selector which I think must be located under the platter. Have you removed the platter to see if yours has the same?
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Old 26th Jan 2020, 6:48 pm   #12
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Default Re: DUAL technical info needed

Quote:
Originally Posted by Mark_RR View Post
The unit in the Radio Museum link has a voltage selector which I think must be located under the platter. Have you removed the platter to see if yours has the same?
I was refering to the unit in post 7 not the OP unit. Michael's advice sounds good but I will have to change the motor cable first as it is cotton covered and breaking up.

Peter
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Old 30th Jan 2020, 10:22 am   #13
Paul Mathew
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Default Re: DUAL technical info needed

Just an update. The speed control arm has a felt piece that rubs against the disc on the motor. This had worn down so much as to become ineffective, so I replaced it with a rubber tap washer which does a reasonable job, although felt would be better. I stripped the tone arm to see why their was no audio (other than that which you could hear directly from the pickup head) The wiring had broken, and replacing this and reassembling was a painless exercise. To my astonishment the audio plays well through one of my DIY SE valve amps. All in all a happy ending! The tx in the pickup head assembly has a selector knob on top, which selects different tappings ranging from 200 - 2kOhm. This makes a difference to the volume.
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