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Turntable Spinning Fast in Reverse

Discussion in 'Troubleshooting and Repair' started by asks-for-boots, Jun 19, 2015.

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  1. asks-for-boots

    asks-for-boots

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    Apr 2, 2015
    A few months ago I purchased a servo turntable from a charity shop for a few pounds, bought a 12V adapter off eBay and used paperclips to connect the adapter plug to the servo plug, and that worked perfectly and still works great to this day. However, I've now bought another turntable from eBay with its cable cut and figured it'd be the same, and it was when I tried the same method using the paperclips, but I decided I wanted to solder the 12V adapter to the inside of the turntable.

    So I removed the cover and stripped out the cord that had been cut (paying attention to the positive and negative orientation). I then soldered the red and black cable to the corresponding cables within the turntable (which are blue and orange). I plugged it in and moved the tonearm across and it now spins very quickly in reverse, and the speed does not change regardless of whether 45 or 33RPM is selected. When reject is pushed it makes a clicking noise.

    I looked on some other forums and it was said that spinning the turntable forward by hand before plugging it in would help, but I tried that and it didn't work. I also tried adjusting the speed screws on the motor, but to no avail.

    I know it's something I've done as when using paperclips the unit worked perfectly well, and the power adapter I'm using is definately the correct voltage (the back of the unit says 11-13V and it's 12V).

    Does anyone know what's wrong with it? I thought I might have the positive and negative the wrong way around but don't want to switch them in case I totally destroy it.
     
  2. shrtrnd

    shrtrnd

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    Jan 15, 2010
    You may have purchased one that actually has electronic component damage this time.
    If you look on the unit's identification plate for the manufacturer and model number, we might be able to find a schematic on it and offer some assistance.
    When you opened the chassis up, did you look around (unplug the turntable when you do this), and look for physical burn damage to any of the electronic components?
     
  3. asks-for-boots

    asks-for-boots

    12
    1
    Apr 2, 2015
    The model is a JVC AL-E31 (BK). I didn't notice any damage and saw that it worked fine when I plugged it in like I did with the Sony. It was only after soldering the cables together. I did damage the mechanics when adjusting the tonearm auto-return because the cover was off at the time, but I got that working again.
     
  4. shrtrnd

    shrtrnd

    3,803
    507
    Jan 15, 2010
    Are you paying attention to whether your 12V adapter is AC or DC
    Were the wires cut before or after the transformer , (trying to figure-out if you're inserting the 12v before or after rectification).
     
  5. Gryd3

    Gryd3

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    Jun 25, 2014
    Can you share any pics?
    Specifications for the input on the turntable as well as output on the power supply.
    AC/DC
    Voltage (range)
    Current.
     
  6. Martaine2005

    Martaine2005

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    May 12, 2015
    Is this the same as yours?

    [​IMG]
     
    Gryd3 and Arouse1973 like this.
  7. Arouse1973

    Arouse1973 Adam

    5,165
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    Dec 18, 2013
    Yep Martin dead give away, DC 11 - 13 V. Nice one, this is the sort of research that is really useful.
    Adam
     
    Martaine2005 likes this.
  8. Martaine2005

    Martaine2005

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    May 12, 2015
    What would we do without Google?

    Incidently, could the OP clarify exactly where he connected his wires inside?
    My thoughts are that 'orange and blue' wires seem more like motor colours.
    Did you connect the 12v direct to the motor?

    Martin
     
  9. asks-for-boots

    asks-for-boots

    12
    1
    Apr 2, 2015
    Yep, that's the model there.
    The adapter says AC/DC (I guess that means auto-switching? Honestly I'm not totally sure with these things.)
    Here's a picture where I've soldered the wires. The positive connects to the motor and negative to the tonearm (which connects to the motor also.)
    The blue wire is soldered to the red and black to the orange.
    [​IMG]
     
  10. Martaine2005

    Martaine2005

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    May 12, 2015
    Great, while youre online, can you post a pic of the power supplies label?
    Have you soldered the wires in exactly the same place as the old wires were?
    My motor wires go to the small board top left corner..

    Have you got a multimeter?
    Very unusual to have a blue as positive and red as negative..
    Martin
     
  11. asks-for-boots

    asks-for-boots

    12
    1
    Apr 2, 2015
    [​IMG]
    I have more-or-less. Originally the wires were soldered to a small board with some metal couplings screwed to it, I removed the wires from this board and soldered the ones from the mains to it, and this is when I had the problem of it spinning fast in reverse. I thought perhaps I'd put too much solder on the connections and this was affecting something, so just removed the small board and soldered the wires together the same as they were before, minus the metal connectors.
    I don't have a multimeter or anything like that, this turntable I bought as a test sort of. I'm not all that experienced in electronics except in computers and thought if it was a quick fix I'd give it a go, but alas. The motor also has a small + and - printed into it here if it helps with the colours

    [​IMG]
    It looks as if the blue is connected to the positive side and red to negative, but I've not removed the motor to check exactly where on the board they're connected, so could be wrong.
     
  12. Martaine2005

    Martaine2005

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    May 12, 2015
    Great, the output of the adapter is 12v DC.
    So, you have 12v coming in and the motor spins backwards.
    The only possible cause it you have wired it backwards... IMHO.

    I would swap them around.
    Martin
     
    asks-for-boots likes this.
  13. Minder

    Minder

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    Apr 24, 2015
    It looks to me like it could be an electronically commutated motor, it has 6 connections entering the motor?
    Obviously a TT is designed normally for one direction and accurate rpm, so it is possible you may have damaged or harmed the electronics by power reversal.
    M.
     
  14. asks-for-boots

    asks-for-boots

    12
    1
    Apr 2, 2015
    I swapped the two wires around and it works perfect now, speed settings and all. I could have sworn that I had them right, but there we go.
    I've not tried it with a vinyl yet so I'm not sure whether the RPMs have been affected or not. It does have settings for fine-tuning the speeds on the bottom though so hopefully that should straighten it out.
    Thanks again for all the help
     
  15. Martaine2005

    Martaine2005

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    May 12, 2015
    Hmm, not sure about that.
    Wouldn't the motor have a 'stator' built in for DC?

    The turntable power requirements are DC not AC..
    Am I missing something here?
    Martin
     
  16. Martaine2005

    Martaine2005

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    May 12, 2015
    Glad you sorted it.
    Don't forget to adjust the motor pots as you have already adjusted them!!:)
    Martin
     
  17. asks-for-boots

    asks-for-boots

    12
    1
    Apr 2, 2015
    Yeah, singles are playing a little too slow now which makes everything sound eerie :eek: I'll have to fiddle about with those!
    Thanks for all the help, I'll know what I've done now if it happens to me again
     
    Martaine2005 likes this.
  18. Martaine2005

    Martaine2005

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    May 12, 2015
    You are welcome

    Martin
     
  19. Minder

    Minder

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    Apr 24, 2015
    Just about all motors have a rotor and a stator, in the case of electronically commutated as in PC (two wire) fans and some of the small 2 wire motors on ebay, they have a PM rotor and an electronically commutated stator and have internal electronics for PWM control.
    A DC or BLDC motor, without some kind of feedback or precise commutation is not much good at RPM control.
    For a portable DC supplied record player I would expect some kind of speed regulation, the mains counterpart has the advantage of a synchronous motor of course.
    M.
     
  20. Martaine2005

    Martaine2005

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    May 12, 2015
    Yes, you lost me for a while.
    I was refering to an ECM. They have a AC to DC converter/rectifier board on the stator.
    That, I think is for AC fed equipment. So what I was trying to explain was that the TT was supplied by DC, therefore no point in a AC to DC board in the motor.
    I am probably wrong, but that's how I understand it.

    Martin
     
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