Modular Power Supplies

[ramphands]

That certainly seems like something is awry.
The PSU2 is the one with the toroidal transformer IIRC.
Are you using the case in a different country to its origin?
Take some photos of the info on the transformer and some board photos. Also check the fuses.

[mrsoundboyking]

I’m in the U.S. and the case came from New Jersey. Not sure where it was before that, if anywhere.

Here are photos of the top & bottom boards as well as the PSU. Not sure if they’re useful in any way.

The seller did include some extra fuses. Do you happen to know where I ought to look for them in the case?

Thanks much.

[ramphands]

Thanks for the photos.
The transformer is unmarked so that’s generally a sign of it being the 115v version, which is correct. The rectifier must be working, and the caps seem fine. Perhaps there’s an issue with the regulators that are under the heatsinks, but that’s conjecture.
The busboards shouldn’t be an issue either, although one of the pins is bent on the -12v side (visible in your second photo) so be careful of that.
The fuse is in the power socket - you can pull out a tray between the on switch and the three-pin socket. It should be an 800ma slow-blow fuse (it will have a “T” marked on it)
You can see this info on page 4 of this pdf:
http://www.doepfer.de/a100_man/A100_short_form_manual.pdf
If you don’t mind, please take a photo of the wiring both to the busboards and to the power switch. Please unplug it from the mains so there’s no live voltage to zap you!
Actually, I’d also visually inspect the pins on the busboards - as one pin is visibly bent, there may be others that are in a riskier position, such as touching each other etc.
Also, when the case is powered up without modules, do the LEDs light on both the PSU board and the busboards?

[mrsoundboyking]

hello, You’re the best, thanks so much for taking the time to think about this with me.

I replaced the fuse (dubious solution) and straightened all bent pins.

I removed all the modules from the case and observed the lights turn on both on the power supply and boards.

I replaced the modules one by one until, in a blaze of solar light, adding a module caused all the modules to not power on.

I moved that module to a different header and everything works OK now.

So, probably a few bad headers in there, which is OK because there are way more than I could feasibly use.

Thanks again.

[ramphands]

You’re welcome!
From a robustness point of view, I’d definitely take out that busboard so you can inspect the reverse for any cold solder joints etc, especially where you were seeing problems.
You could also try continuity testing the boards to see if there are any broken traces between headers.

[perbarfot]

So, I’m trying to install a power supply unit and a bus board into my eurorack case. But the instructions are kind of vague, and I’m a noob. So I wonder:

1. I want to connect the power inlet cables (black +, white -) into the input terminals on the PSU. But there are two + inputs and two - inputs. Does it matter which ones I use?
2. I want to connect the PSU to the bus board (gnd to gnd, +12v to +12v, etc). But do I really need to connect the +5v cable when my system doesn’t need that?
3. The bus board has two sets of terminals. Does it matter which one I use? Should I use both?

Thanks!

[chalkwalk]

Are the power inlets from a wall outlet (i.e the board has a transformer) or a lower voltage AC or DC supply? In the former case the two wires are potentially to allow you to use two lower gauge wires. In the latter case (for an external DC supply) it may be to connect two up at once (to double the available current). In the latter case you can connect to either terminal, as long as you get +ve and -ve correct.

As for connecting up the 5V, I can’t see why you wouldn’t: it’s trivial and the day you try a module that needs a 5V supply, you’ll end up less confused about why it’s not working. Modules can exhibit very strange behaviour when partially powered, so I’d just connect it up.

I presume the two sets of terminals on the bus board are to allow easy connection from a supply whichever side you mount it on (though you could theoretically connect two power supplies to a single board): I’d only wire up the closest one.

[perbarfot]

The PSU is powered via a power adaptor (18V, 60W, Mean Well GSM60A18-P1J). I suppose that would be “a lower voltage” in your example, and I can connect to either terminal.

Thank you so much! Your answers were very helpful! I’ve never done this before, and want to make sure I don’t accidentally destroy my modules!

[perbarfot]

A final question. I’ve now connected everything, but the LED’s on the bus board shine red. I would expect them to be green if everything is OK.

I’m using this bus board: https://modularsynthlab.com/product/eurorack-bus-board-msl-filter-bus-board/ But there is no information on colors of LEDs as far as I can see.

I use the recommended power adaptor. I’ve connected power inlet cables to PSU (+ to +, and - to -). And I’ve connected PSU to bus board (gnd to gnd, +12 to +12, etc).

Do I dare to connect a module to see if it works?

[mode.analogue]

Well, I suppose you might want to try using a multimeter on some of the power headers first before frying some of your modules in case you’re unsure about your connections. I would even be tempted to recommend checking with a multimeter even if you’re sure about what you are doing. That way you just make double sure that everything went well and without any costly confusions.

As for the LEDs: they might as well be red ones. Many bus boards are actually using red LEDs. It’s not necessarily the colour which counts but that they are lit evenly and at all…

[perbarfot]

Good idea, I’ll do that, thanks!

[chalkwalk]

Agreed: considering that the only power provided to the bus board is from the power supply, it would be significantly more complex to provide “power inspection features” (since powering the board incorrectly wouldn’t allow such features to operate) beyond the power indicator LEDs. Instead these 3 LEDs, along with appropriate resistors, run between the three power lines and ground. The appropriate resistors mean you get the required current for maximum brightness for each LED. If the power is incorrect (e.g you swapped 5v and 12v or -12v and ground) one or more LEDs will be a noticeably different brightness to the others (brighter, dimmer or off). This won’t catch all possible problems, but it will catch you accidentally interchanging the power leads.

As was said: The best bet is to use a multimeter. Note: I recommend against testing directly on the headers (it’s very easy to short circuit things like this). Instead plug in a (ideally 16->16) power connector (like you’d connect a module to) and confirm the voltage of each pin reference to ground. Typically I do this in two steps, first I check for continuity between the 6 ground pins when unpowered. I then power the system and check the voltage between any ground point and all 6 power pins: the end two by the red stripe in the ribbon are -12V, the next 3 pairs from that end are ground, the next pair is +12V, the next +5V. The next two pairs won’t be connected to the power supply, so you can ignore them for these proposes. If the voltages are okay (including polarity), then you are good to go.

[perbarfot]

Thank you so much for your detailed answer!

[VascoLe]

Anybody knows where I can find these? They’re sold out everywhere and Malekko isn’t responding to the messages on their websites for a while now. I don’t even know if everything is good since the pandemic hit, hope they’re fine above all.

If anyone knows where or when these power supply will be available, I would appreciate it, been trying to get one since late 2019.

[Jfkimmedy]

Not sure if this has been discussed before, but does anybody know if it’s okay to push the power supply to it’s limit? My Uzeus can go up to 500mA at -12 and with some new modules arriving in a few days I’d be at 497mA according to modulargrid. Now I heard that you shouldn’t push the power supply over 80% of its capacity because some module draw more power when they start up and that could “overpower” the PU in some way? Is that true?

[chalkwalk]

Potentially, plus it’s also true that power supplies’ quoted maximum allowable current is often optimistic for long term use. The lower your percentage utilisation, the longer the expected lifespan.

[mattlowery]

Is there any downside to leaving a eurorack case’s power switch in the “on” position and using a power conditioner as a master power switch?

[SMesquida]

I guess that there are better power solutions than others. Maybe in terms of lower noise, for example. Do you know if one of these power solutions is better than the other one?

Befaco vs Clank.

I want to purchase a new case and the power solution may conditionate my decision to one side or another.

[renegog]

I’m happy with my Clank power supply (as mentioned in the cases thread they’ve added i2c to the board which I think might interest you!). I have not noticed noise coming from the power supply, but I don’t have too many power hungry modules, I have a fairly small system and am not taxing the power supply too much overall (having enough power is probably the most important factor and the clank is way more than enough for 6U 70hp that I use) — I have even used a 64grid with legacy monome modules and the power supply takes it without a problem. I also don’t care a whole lot about a bit of noise and I don’t have something to compare it to, so when I say I don’t notice it please do take it with a grain of salt

I have heard that having the power headers in series (like with flying bus boards or the befaco boards I’ve seen) is more likely to introduce noise. I’ve also heard that it doesn’t matter because switching power is so inferior that it will always be relatively noisy. Personally I think I’d be perfectly happy with Befaco power (was doing okay with a uzeus before…), but the Clank does seem higher spec’ed—maybe they just have better marketing-speak on their website, lol.

[SMesquida]

Thanks for the detailed response! I’ll take that in consideration when I purchase my next case.