30 W wall wart! I tried Googling the model number but only got a bunch of Chinese sites. FC recommends 1 A (12 W) per FC Power board, so that should be easily good enough for two.
Looks great, thank you!
I just want to add that I have encountered someone on the Facebook group with the exact same problem, which was solved with the exact same fix. Just to confirm it wasn’t a one-off issue.
In @THOGRE’s design, I recommend changing D8 (from +12 V to ground) from a 1N4004 to a 1N5817 or similar Schottky; see posts starting here. D4 (-12 V to ground) can stay a 1N4004, or I think probably can be left out entirely as talked about later in that thread.
Oh wow this was the exact problem i was having I’m going to try this because i built 2 routemasters and was having this problem. Tried it on 3 other power supplies i had the 2 routemasters tried a 2000ma ww a 1000ma ww a bunch of combos. Im going to give this a try thank you
Hah, I think you also found my reply on reddit? Happy to hear you fixed it!
Hi there everyone, I am just getting started DIY synth-ing around, and decided to start here. I’m working on a variant of the MFOS/FC-Power style wall-wart power supply (trying to sharpen some of my skills, and teach myself PCB design). Before I go all-in and build a bus-board for my synth build, I wanted to see if some of the great folks in this community could sanity-check my connector choice.
I see that eurorack seems to use 10 or 16-pin cables for power distribution. I don’t plan to use any eurorack modules myself. Is there any reason not to use a 3-pin connection for power? The three pins would be +/- 12V and GND. I was thinking of using this sort of connector.
I don’t think I need a 5V rail, but maybe it’s best to leave room for one? In that case I think I would still only need 4 pins. Am I missing something basic here? Why so many pins standard (many of them are GND in eurorack, for instance)?
Any help is appreciated. Thanks!
After posting this I found this: Power supply connector - #3 by analogoutput
My question is (at least partially) answered there. I think I will opt for a few more pins to support potentially adding 5V/3.3V in the future, even though I doubt I will need it.
Over there I said
Uh… no. It has to carry the difference between the positive and negative rail currents. I guess the reason for multiple ground wires is to minimize the impedance back to PSU ground.
If I were doing it all over I think I might opt for MTA-156 or MTA-100 — like some of the ±15 V formats use, but I’d probably stick with ±12 V just because there are more module designs out there that use those voltages. I’d be inclined to keep it simple and not add wires for other voltages or future use. But that’s me.
One thing I’d definitely recommend is using a connector/header combo that (unlike IDC connector and unshrouded pin header) cannot be plugged in backwards or offset.
Completely agreed with your point about using connectors that can only be plugged in one way. And since posting my last comment, I reversed my choice on adding a 5V rail. I’ll keep it simple and add 5V regulator stages to any modules that end up needing it. I think for me this will just be an arduino-based MIDI-to-CV.
Anyways, thanks for the help and I will definitely post back with my results! I think I’ll follow your lead and start documenting my work and open-sourcing my schematics, gerbers, etc.
I have used three pin JST-XH connectors in all my recent builds. No issues so far!
Oh, and one other advantage to Eurorack headers, if you get fabbed PCBs… since a lot of people use them, it’s easier to sell off extra PCBs that use them…
Though you can do something like what Barton does, they use overlapping Euro and MOTM header footprints.
Or you can make little adapter boards to attach Eurorack (or other) headers to boards that lack them:
+1 to the answer by @savt22 above. I too have used JST-XH connectors (3 pin for +/-12V modules, 2 pin for +9V modules), without any problems. Apart from being smaller which is a plus for small builds, I like the fact that I can find corresponding female connectors with 20cm colour coded hook up cables that are either an open ended or have female dupont connectors at the other end. Great for use with male headers connected to Arduino pins, breadboards, or places where you’d normally have a box connector too. They also come at 1/10 of a price of a 2x5 ribbon connector at my local store. 
The best reason to stick with the eurorack connector is so you can build and share modules with other members of this community. The whole reason for standardizing is sharing.
Agreed! If one designs (and shares) gerber files for PCBs, it makes more sense to follow a well established standard. However, if one builds (and shares) on stripboard like I do, it is trivial (i.e. easy) to change the layout from one connector to another. In the end DIY is asmuch about sharing as adapting designs to your individual needs 
I just ordered some of @analogoutput 's Wall wart ±12V power supply to be printed, I want to run two in parallel.
My current setup with around 16-20 modules is causing power drop outs and noise on my Twin T Drummer. I haven’t figured out the exact power draw of all my modules, although this post on usage and @analogoutput 's gitlab pages have been very helpful!
I’m looking at getting a 12v AC 2A power adapter, something like this UK one on ebay, I’m in Australia right now and it’s hard to find anything over 1A (if anyone knows of one let me know!)
I think this is the setup to have two power supply’s wired in parallel, does it make sense?
I actually didnt think 2A ones were available here in the UK, thats good to know. 
There is a company in Greece called Amarad Hellas that makes AC wall-warts with various voltage ratings (12V included) at 2A. I recently bought a 9V of theirs at 2A from a local shop for something like 15 EUR, incl. VAT. They seem to take direct orders so you can try their website or their tel number to see if they ship to Australia and for how much. Or maybe ask them whether they export to any shops there? If you dont have to pay the 24% VAT then it might make sense financially, but beware, these things are heavy!
Also, hasn’t Australia banned the sale of linear power supplies? Make sure you don’t get into trouble by importing stuff!