Background
Most cassette players do not have a speed control function, but thanks to the design of (most.. probably all but don't quote me) tape players, it is easy to add.
Cassette players have a trim potentiometer (also known as a trim pot or trimmer), which is used to fine tune the speed of the motor when being assembled. Trim pots are variable resistors - their resistance can be set by twisting a little screw. If we replace this component with our own variable resistor in the form of a twist potentiometer and then place it on the outside of the tape player, then we can control the speed of the motor on the fly by simply twisting a knob.
So grab your tape player and lets do it!
You Will Need..
- 1 x Tape player
- 1 x Twist potentiometer or slide potentiometer (in the 10k - 20k range. Most common ones should work)
- Hookup wire
- Soldering iron / Solder / Flux
- Small screwdriver(s)
Steps
!! Only use low voltage battery operated units unless you know what you are doing (no wall outlet voltage = much safer) !!
Obtain a tape player. This one was from the thrift store. REMOVE THE BATTERIES.
Unscrew the case. You may need to peel up rubber feet / remove clips / etc.
Find the main circuit board. If you don't see a trim pot (see next few steps), then unscrew the board and flip it over.
Locate the trim pot. This is a variable potentiometer used to tune the speed of the motor at the factory - aka a built in way to adjust the motor speed. We want to remove this and replace it with a normal twist or slide potentiometer to make it easier to adjust on the fly.
Clip the trim pot from the board, or desolder it.
Locate the solder points for the trim pot on the back of the board. Solder one wire to each (3 in total).
TEST: Temporarily re-insert the batteries and press play. The motor should spin at full speed if all went well. Test shorting the wires together. Some combination should either stop or slow the motor.
Find a way to feed the wires back out of the tape player and re-assemble. You may need to drill a hole. I got lucky with these holes for the clip on the back.
Attach the three wires to your potentiometer. The trim pot had 3 connectors: 2 on one side, and 1 on the other. Connect the one on a side by itself to the middle pin of the potentiometer. (blue wire in my case).
NOTE: If you don't want to think about it, just try all of the combinations until the twist pot controls the speed.
You're done! Here is one I built and 3D printed a case for to house the controls. This one has 2 twist pots in series (messing around trying to get better control), an on/off switch for the whole player, and a "max speed" switch to completely bypass the speed control.
You're done! Here is one I built and 3D printed a case for to house the controls. This one has 2 twist pots in series (messing around trying to get better control), an on/off switch for the whole player, and a "max speed" switch to completely bypass the speed control.
Tips & Other Notes
- Insert the batteries and test often to make sure you didn't break something.
- For portable style tape players like mine, you usually don't need the front clamshell at all. In both of mine I snapped it off to get that open-faced look.
- If you are using an old tape player like me and have issues with it not having enough power to play a tape, your belts might be the issue. Google "cassette belt kit" and you should find cheap packs of them.
