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.
![5 V adapter schematics](http://syntherjack.net/wp-content/uploads/2016/08/5V-adapter-schematics-syntherjack.png)
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.
![Adapter PCB with values (red = TOP = copper side)](http://syntherjack.net/wp-content/uploads/2016/08/5V-adapter-PCB-values-syntherjack.png)
The PCB fits into heatsink (V7110 type), so the completed device looks really neat. I used thermally conductive silicone pad under the voltage regulator.
![5 V adapter, front view](http://syntherjack.net/wp-content/uploads/2016/08/5V-adapter-front-syntherjack.jpg)
![5 V adapter, side view](http://syntherjack.net/wp-content/uploads/2016/08/5V-adapter-side-syntherjack.jpg)
![5 V adapter, front view](http://syntherjack.net/wp-content/uploads/2016/08/5V-adapter-front-syntherjack-1.jpg)
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”
Jack
Hello!
Is just needed to connect 1 ribbon from my bus board to this 5V adapter?
thanks
Question: i saw this video where a 12V voltage is converted to 9V using a single regulator, no other parts included. Used to hook up a guitar pedal (stompbox) to a Eurorack setup. Would you advise an additional heatsink for that? Video: https://www.youtube.com/watch?v=7Ik18N_G-w4