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Convert 15v turntable to 12v

Discussion in 'General Electronics Discussion' started by bloodaxe, Jun 7, 2016.

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  1. bloodaxe

    bloodaxe

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    Jun 7, 2016
    Hello.
    I am a total novice and I need some help.

    I have a hifi turntable with a 9vdc motor and a 15v input. Why it's 15 I do not know.

    Without beating around the bush I want to run my turntable on 12vdc. I can explain why but it's somewhat irrelevant.
    So how would I go about this? Is it as simple as changing a transformer?

    Many thanks in advance for your help.

    In case it's important, it's a Pro-Ject Debut Carbon Esprit with speed box (DC motor, auto speed selection)
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Weclome to EP.

    I see 2 ways:
    1. Try whether it works on 12V without modification. If so, you're done.
    2. Get a so called boost DC/DC converter or step-up converter like e.g. this one.
    Note that a DC/DC converter operates by swtching the DC, then smoothing it with a filter. Depending on the quality of the converter some residual noise from the switcher may be present on the DC. This may or may not have an influence on the audio quality, again depending on the quality of the turntable's power input circuit. Additional filtering may be required.
     
  3. davenn

    davenn Moderator

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    maybe there's a 15V to 9V regulator in there ..... wouldn't be surprising as the turntable would need a very stable voltage to avoid warbling in the music
    caused by fluctuations in the voltage to the motor ( if a regulator didn't exist)

    without more info on the turntable ... any other comments would be just guesses


    you probably mean a buck converter ( not boost) to take the 15V to 12V


    Dave
     
  4. hevans1944

    hevans1944 Hop - AC8NS

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    Nope, it already runs on 15 V and OP wants it to run on 12 V. I like the idea of hooking it up to a 12 V DC power source to see if it still works at the reduced voltage. But, as you noted, more information on the turntable would be necessary for a definitive answer.
     
  5. davenn

    davenn Moderator

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    no, read the OP ... it's a 9V motor, then reconsider my comments ;)

    Between the 15V in and the 9V motor, there will be a voltage regulated speed controller for 33, 45, maybe 78 records that has a 9V output to the motor

    first step would be to see if the speed controller runs happily on 12V

    D
     
    Last edited: Jun 8, 2016
  6. Bluejets

    Bluejets

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    According to the link (if I have the correct one) the speed box is 16V AC in and out.
    Perhaps be a bit more specific on the model?
     
  7. davenn

    davenn Moderator

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    which link did you look at ?


    googling the name he posted Pro-Ject Debut Carbon Esprit

    I got this .....
    http://www.project-audio.com/main.php?tech=debutcarbonespritdc&cat=default&lang=en



    tis just getting more confusing hahaha .... I may yet be wrong with the earlier comments
    I think it all pins around this auto speedbox thing that seems to be an optional extra


    Dave
     
    Bluejets likes this.
  8. Harald Kapp

    Harald Kapp Moderator Moderator

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    of course, thanks for putting this straight, Dave. There have been so many questions lately for boosting a DC voltage that I became a bit confused.
     
  9. davenn

    davenn Moderator

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    don't panic too much .... as I said I could still be wrong haha ( we all could)

    depends on this auto drive thingy ;)


    D
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Oh, please do explain why you want to run your turntable on 12 V DC. Let us be the judge of what is irrelevant.

    Also please explain why you think the turntable motor operates on 9vdc when the manufacturer's literature says the turntable motor is a synchronous AC motor that gets its power from the mains through a transformer and a separate 15 V DC power supply driving "an ultra precision frequency DC-driven AC generator" and provides a two-frequency drive signal to the motor? You may be a total novice, but I am totally confused as to what you want to DO and WHY you want to do it. Is the goal to replace the mains-operated 15 V DC supply with a 12 V battery?

    Just FYI, if a turntable motor operates on DC, i.e., a DC motor whether brushless or not, it would need a sophisticated feedback control system with some sort of tachometer to sense motor rotation speed for comparison with a precision frequency source. Not saying no one has ever built such a beast, but a synchronous AC motor by design provides a rotation speed that is exactly proportional to the frequency driving the the motor. This driving frequency is typically the power-line mains frequency (50 Hz where you live), or it is derived from a quartz crystal oscillator if you use something like the Speed Box accessory for AC operated turntable motors.

    Every line-operated clock keeps perfect time because they are driven with some form of synchronous motor. The utility providing power ensures that the total number of AC cycles provided on the mains is corrected to exactly the right number of cycles once per day, ensuring clocks never gain or lose time over long periods. The super-sensitive ears of audiophiles may be able to detect short-term variations in power-line frequency, so there is a market for quartz crystal oscillator control of the motor driving frequency. A side benefit is the capability to slightly vary the motor rotation speed to accommodate both 33-1/3 rpm and 45 rpm. However, it is too big of a stretch to increase the motor drive frequency high enough to accommodate 78 rpm, so an auxiliary (larger) pulley is required on the motor shaft pulley that belt-drives the turntable pulley.

    You may be able to un-plug the 15 V DC power pack and substitute a 12 V DC power source without modification. I would try this first. If the motor refuses to run on the lower voltage, you will need to replace the 15 V DC mains-operated power supply with another power supply that accepts 12 V DC and produces 15 V DC. Google is your friend here. There are plenty of DC-to-DC power supplies for sale on the Internet that operate from 12 V DC and provide 15 V DC with at least 0.8 A capability. More amperes capability is okay (the turntable will only use what it needs) but don't go overboard and get one with more than one or two amperes output capability. Perhaps this one is appropriate to your needs.
     
    Harald Kapp and davenn like this.
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Did I read that some of our members are confused as to what 'exactly' our new member (bloodaxe) is trying to accomplish? If so this has never happened before! :p

    There are times I wish I were a psychic!

    Chris
     
  12. hevans1944

    hevans1944 Hop - AC8NS

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    Psychic is good. I live with one every day. Her favorite remark to me is, "I told you so!"

    And I do love it when a newbie pops in with one post and then goes on vacation without further comment while receiving ten replies. Gives me a warm fuzzy feeling all over to know how much good this forum is doing for the general public in taming their fears and interactions with those pesky (but useful!) electrons. :cool:

    Y'all come back, you hear! (Just spent a week in the American South... Kentucky, Tennessee, Georgia, Florida... they really do talk thet way down thar.)

    Hop
     
  13. davenn

    davenn Moderator

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    @bloodaxe

    Im closing the thread
    if you ever come back with more info and want to continue ... PM me and I will reopen the thread
     
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