The central instrument cluster on a classic mini and many classic cars utilize a mechanical voltage regulator (stabilizer) to provide a constant 10v to the instruments. Variance in the supply voltage will cause an internal bimetallic strip to change shape making the internal contacts connect or disconnect ensuring a constant 10v is supplied. Overtime the mechanical nature of the regulator can wear causing failure and an unreliable voltage output. The convenience and cheapness of modern electronics makes it possible to replace the mechanical regulator with a solid state unit i.e. no moving parts.
Circuit diagrams for solid state regulated power supplies are readily available on the internet. My circuit utilizes a LM7810 10v voltage regulator protected by a diode and two electrolytic capacitors to smooth input and output from the LM7810. The LM7810 is grounded via the circuit board and physical connection to the mini speedometer. This also serves as a heatsink to ensure the regulated is stabilized allowing up to 1amp current to flow without overheating.
I have added optional ground wires to the input and output. The grounding through the mounting hole will be sufficient, however the addition of the ground wires allows more options for connecting components to the regulator.
A simple PCB was designed in DipTrace and sent off to OSH Park for manufacture. Turnaround times are approximately 3 weeks delivered to the UK if you select the free shipping option. I was in no rush so happy to wait and save on shipping costs.
A stack of PCB's arrived in the post a few weeks later ready for soldering. I also 3D printed a small case to enclose the PCB to avoid any of the solder pads shorting out on the metal of the speedo housing.