Finished Pieces

motor speed mod


      -LM317 adjustable voltage regulator
      -5k pot
      -240 ohm resistor
      -.1uf capacitor
      -.01uf capacitor (.1uf will work too)
      -small perf board (to build the circuit on)


      -de-soldering braid
      -needle nose pliers
      -medium size flat head screwdriver
  • 1 open housing
  • 2 remove main circuit board
  • 3 remove black plastic tape deck cover
  • 4 There is an opening in the motor housing where the power wires are soldered. Wedge a flat head screw driver in this space and turn it to pop the cover off. Don’t worry if you crack the circuit board, you’ll be removing it shortly.

    Underneath the cover is a little circuit board. This is a motor speed regulator. This was installed to ensure that the motor maintains a consistent speed. You will be removing this and installing your own ADJUSTABLE speed regulator in the Barbie housing.

  • 5 Use a de-soldering braid to COMPLETELY remove the solder from the two points shown. This will reveal two tabs sticking through the board. If you have removed all of the solder you should be able to wiggle the tabs around freely
  • 6 Next you’ll be removing the circuit board. This is an important step and should be performed with care. The tabs sticking through are connected to the motor itself. You want to remove the circuit board without damaging these tabs.
    The tabs are flat and were pushed through a rectangular hole in the board. Then the tops of the tabs were twisted to lock the board down. What you want to do is twist the tips of the tabs so they are flat again and will slide freely through the rectangular holes.
    Use a pair of needle nose pliers to do this and bend them carefully so they don’t break off.

  • 7 Solder two wires to the points shown in the picture. It’s a good idea to use colored wire so you know where to attach the wires later. Red is positive, black is ground. The black wire is connected to two points. One is the tab farthest in and the other is a small peg connected to the motor housing. Connecting the black wire to this point grounds the motor housing. If you don’t do this, the magnetic field generated by the motor will create a considerable amount of noise in the main audio mix.
  • 8 Push the cover back on and put it all back together.
  • Sounds

    Sorry, no sound files for this piece.

    5 Responses to “motor speed mod”

    • 1 » Archive » Barbie Bending Update! said:
      August 24th, 2006 at 1:48am #

      […] Something you’ll be seeing a lot more of in the near future is schematics and bending info for popular pieces. The one piece I get the most emails about is the Barbie Karaoke Machine, so that’s what I’m starting with. I’ve added a new page to the “finished pieces” section called Barbie Bending. So far I’ve added info on bending the echo IC in the BKM and a step by step tutorial on installing a high quality motor speed control. […]

    • 2

      GetLoFi » Barbie Karaoke Machine Circuit Bending said:
      September 15th, 2006 at 8:49am #

      […] Pete of recently updated his website to include a blog. The very latest entry is a nice virtually step by step guide to circuit bending a Barbie Karaoke tape machine with echo effect. These rather pink devices are readily available on eBay for cheap. The resulting sounds are devastating to say the least. The tape motor control mod is also posted and I am sure can be applied to any tape device. The key appears to be the use of a voltage regulator, which outputs a steady voltage without effecting the rest of circuitry too much. […]

    • 3

      Art of Science said:
      January 20th, 2013 at 5:44am #

      As the author says, this WILL WORK. But the motor speed will no longer be regulated, as it is originally. You’ll find yourself constantly correcting the speed, not to mention anomalous Rew and FF. You’ll probably have wow and flutter you can’t fix. And in the occasional machine with electronic motion-sensing auto shut-off, it will auto shut-off at slow speed. This makes me think I should start selling adjustable speed motors! (I’m not kidding.)

    • 4

      casper said:
      January 20th, 2013 at 4:51pm #

      AOS: thanks for the very true info. This is indeed a very clunky way of regulating motor speed. REAL motor speed regulating circuits, like the one I suggest removing and replacing in this tutorial, have lots of extra components for regulating current and watching for problem states. SO if precision is important this method may not be for you.
      BUT for experimental sound stuff, quick, dirty and cheap will get you there…

    • 5

      Pat said:
      September 9th, 2013 at 11:56pm #

      Hey Pete,
      Using this modification to slow down another tape player, is there any way to smooth the taper control out across the pot? i.e. all the speed change occurs in the last 1/10 of the turn….. Its a little better with a 1k pot.. but maybe theres a smoother way.
      Thanks for the info

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