Some eurorack modules still use +5 V voltage busboard rail. If your PSU doesn’t supply it, you need to get a 5 V adapter (or get a new PSU). Doepfer “low cost” adapter costs around 15 euro. My alternative is much cheaper – project is very simple and all parts costs about 1 euro (but you scarifice your precious time to build it – f. e. if you are a NASA pilot, this one can cost you hundreds of dollars 🙂
Adapter uses common 7805 voltage regulator in TO220 and 2 capacitors. In theory it can supply 1,5 A of current, but taking relatively small heatsink into consideration it will be much less. Remember, the 5 V is regulated from 12 V rail, so if you take 100 mA from regulator, that means you got 1,2 W from PSU and wasted 0,7 W for heating your system.
Voltage regulator with heat sink are mounted on the copper (TOP) side of the PCB, capacitors and 2×8 power connector on the BOTTOM side. This way you don’t have to etch double-sided PCB, you can also use this design (see attachments under this post) to move to prototype PCB.
The PCB fits into heatsink (V7110 type), so the completed device looks really neat. I used thermally conductive silicone pad under the voltage regulator.
I have tested it, used it, works great, but I must say:
“This is a part of an eurorack power supply. Use this project for your own resposibility”