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Can I use a simple zener circuit to step down voltage for a turntable motor?

tom1970

Aug 23, 2021
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I have been given a broken JAM turntable which has a USB/digital output. The main board is basically a write off but the motor, speed selector switch circuit and transformer/power-in circuit seem to be working ok so I want to convert it to just a simple analogue-only record player.

The motor is a 9V/12V pretty much like this one...https://www.aliexpress.com/item/1718665975.html
but the transformer and power board (bridge rectifier and filter cap) puts out 20VDC (previously it supplied the main board which then fed the motor with the required voltage (12VDC).

So basically I was thinking I could use a 12V zener diode to regulate the voltage to 12V to then supply the motor. Would a circuit like this work (call it 'circuit A')...?
simple zener.JPG
I was thinking if I get a 5w 12V zener then it would have a max current of around 410mA so the series resistor would have to be around 20ohms if Vin is 20V. Can it be that simple or am I missing something?

Another circuit I was looking at (call it 'circuit B')) was this one ... https://theorycircuit.com/12-volt-regulated-power-supply-circuit-using-zener-diode/ ... which specifies motors in the description. I'd have to change some of the values here as this is 15V to 12V. Also I don't know what the transistor is for in this one...?

Any thoughts gratefully received...

Tom.
 

Bluejets

Oct 5, 2014
5,991
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Oct 5, 2014
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5,991
No.
As an added note, these motors usually have some kind of on-board speed regulator.
Hence supplu voltage 8.4 to 16 v dc.
If you need to reduce voltage go for a step down converter.
Couple of dollars each off Ebay or whatever and can usually handle an amp or two.
 

tom1970

Aug 23, 2021
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Aug 23, 2021
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Thanks for the suggestion. I didn't realise those things were so cheap. Feels like it's cheating a bit though!
 

tom1970

Aug 23, 2021
28
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Aug 23, 2021
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Strange reply.... o_O
Yeah I mean using a pre-built circuit rather than constructing something myself - so I feel like I'd be cheating a bit.

I was originally hoping to convert this turntable using only recycled stuff but it sounds like the step- down converter is the simplest and most reliable option. Thanks again for your help.
 

Bluejets

Oct 5, 2014
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Yeah I mean using a pre-built circuit rather than constructing something myself - so I feel like I'd be cheating a bit.

Whatever floats your boat I'd imagine.
I know which way I'd be heading, and it's not roll 'yer own. :)
 
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