Plug-in power supply for the Commodore 1541-II


This is a plug-in power supply for the Commodore 1541-II floppy disk drive. It's a bit of a spin-off of my 250466+ board as I re-used the overvoltage protection circuit and 5V creation from this project and put in on a small PCB that can be plugged directly into the power supply connector of a 1541-II. As for the 250466+ board, there is only a 12V DC power supply needed.



As this is a direct copy of the circuit used in the 250466+ board, it's also based on through-hole components. Then again, using SMD components would not have saved much space anyway.
The schematic is taken 1:1 from the 250466+ board:

The reverse current protection is realized through the body diode of the N-FET Q1 and the FUSE F1.
The over-voltage protection is implemented using a voltage reference TLE431 and a comparator TLC3702 (with push/pull output) which triggers the FET to blow the fuse. There is a 15V Zener diode in the supply of the comparator to protect both, the comparator and the FET's gate from higher voltages.

If the voltage rises above ~13.3V, the output of the comparator jumps from ground to its supply voltage. This triggers the FET which creates a deliberate short circuit to ground to blow the fuse.


I designed a 3D printed case with FreeCAD that consists of two parts held together using self tapping M2 screws.


The FreeCAD design files and STL files can be found in the repository.

Hints and Links


All files related to this project can be found in the BitBucket repository

License Information

This is a spare time project I did without any commercial interest.
Everything is released under the Creative Commons CC-BY license.

Creative Commons License

In a nutshell this means that you can do share, modify and use everything released under this license even for commercial projects.
You just need to give me appropriate credit, indicate what changes you made and agree not to try to force a more restrictive license on my work.
See the CC BY license for details.