In this tutorial, you can find a step-by-step tutorial about how to rewire a Rega tonearm with a VTF knob, like the RB300, RB301, RB330 and others.
If you want to rewire a Rega RB tonearm without the VTF knob like the RB250, follow this link https://youtu.be/3RCeKr7ziCQ
The rewire kit shown in the video is available at The Vinyl Source https://www.thevinylsource.co.uk