06/18/2025 – Recently updated with better explanation.
Here is a stripboard layout that I did for cassette player speed mods. It is based on a drawing from the old Casper Electronics website. It only requires a small piece of stripboard (4×6 ) and 5 components. I am sure that there are other ways to affect the speed of a tape player motor but this design has served me well over the years. Works best on tape players, some tape recorders can be a little more finicky and require a little more finesse.
After you build the board, remove the cap (see picture) of the tape player motor, desolder the old board and remove it.
The two tabs that remain on the motor are where you will connect the motor ground & motor power.
If it doesn’t work the first time, and you sure you have made the small vero board correctly, try reversing the motor ground & power wires.
The vero board doesn’t fit inside the motor like the old control board, so find a place to mount it inside the tape player case.
Always test before drilling holes or re-assembly.