Hello,
I use the FrecuencyCentral power supply PCB LMNC also used in his video about building the case. It worked fine for a while while usung my modules. But now when I put it on there is a constant low harsh hum and my oscillator (AS3340) doesnt work anymore. When I plug my oscillator in another power supply it does work.
Could there be something wrong with my power supply? If so, what could be the problem?
Could be pulling too much. Try unplugging some stuff and trying the oscillator again
The oscillator is the only module in there now. I took everything out earlier.
It also worked before with more modules in it.
I once had a bad cable going from the module to the power rail (the module still works). Perhaps it broke something in the powersupply?
So it works with your other modules but not the oscillator?
I would use a multimeter to make sure +- 12 is coming out
Sorry if I was unclear. But I have two rows in my synth with each another power supply (the pcb from frequency cenrtal). On one layer everything just works fine. And on the other I hear a loud and low hum and the modules dont work the way they should.
I tried some combinations of modules on each layer and the kind or amout of module doesnt matter.
I also measured the voltages but that also isnt the problem.
Thats why I think the problem might come from the circuit on the pcb power supply. 
Are they powered from the same wall wart?
Yes they are. The wall wart is connected to some stripboard and from each line on the stripboard two wires go to the pcb.
I dont know if thats how you are supposed to do it🤷♀️
A loud humm can be a sign of:
1: the voltage regulators not working properly. I had a CD-player once in which the regulators got so hot, that they desoldered themselves. The effect was, that the output voltage was still present but not regulated anymore. The humm was caused by the voltage drop on the buffering capacitors at (high) load.
2: the buffer capacitor(s) not being connected or broken. As an effect you get a 100 Hz / 120 Hz humm because the AC is converted to a ‘pulsing’ DC and the voltage will not be stabilised.
I checked those things but everything looks fine (as far as I can see).
When I connect my modules to the broken power supply the leds slowely go off and the loud and low humm fades away after a while. The cables to the modules also get warm
Its kinda weird because it worked fine before.
I found the problem. Turns out I mixed up the ac input of the power supply. Thank you so much for helping me!
That should NEVER happen. Cables only get warm when they conduct a large current, and in kosmo or eurorack that never happens to an ordinary module.
What do you mean by that?
I have two power supply pcbs from frequency central. They are both connected to the same wallwart. But the cables from the wallwart went to different parts on the pcb.
So one ac cable went to ac1 on the pcb and on the other pcb to ac2.
Well, I hope all problems are gone now and nothing got fried.
That means you shorted the AC input to ground. Probably your wall wart went into some form of overcurrent protection. Consider yourself lucky and be more careful next time.
Oh okay, Im quite new to working with ac😅.
Just to check, is there any difference between ac1 and ac2 on the pcb? One wire from the wallwart has grey lines on it and one is completely black.
One of them is connected (on the PSU board) to DC ground and the other isn’t. Which connects to which wall wart wire doesn’t matter if there’s only one PSU board, but if you connect a second PSU to the same wall wart, you have to connect the same wall wart wire to AC1 on both and the other to AC2 on both. Otherwise the grounds on the two boards are at different AC voltage with respect to each other and if you try to connect both boards to a common ground in the synth, bad things happen. Basically you’ve then shorted the wall wart.
The way these PSUs are constructed, one of the “AC in” points goes to ground, the other goes to two half-bridge rectifiers to make the two supply rails. As inverting a sine wave is equal to phase shifting it, it doesn’t matter in which order you connect them. Another way of seeing this: both halves of the sine waves get rectified, so it’s polarity is irrelevant.
But, as one of the AC connections goes to ground, and the grounds of different PSUs connect together (they should in your case. Even if you didn’t, they will connect through the patch cables), you must use the same order on each PSU board. Otherwise, the two poles of the AC connection will be shorted through your PSUs. A wall wart might have a protection against this, a transformer will overheat and form a fire hazard.
Just to be complete, on some PSUs you will find AC1, GND, and AC2. These are designed to use a centre-tapped transformer. You can use these with a single phase transformer or a wall wart by connecting AC1 (or 2) and GND, in which case all the above applies. When using both AC connections with a centre-tapped transformer, the order does not matter.
In case a video helps:
Moritz Klein does a very good job of explaining how it works.
And also if you have added in the future another case, with another wallwart, remember to connect the phase and the neutral of the AC like the one you just made, if not huuummm also