Hi all,
I’ve gotten some really great advice here so far, so I thought I’d seek further advice on some power issues with my modular. I have everything plugged into a single power strip, and when I flip the whole thing on, the 5v rails on my power supply work fine but the + - 12v rails aren’t giving off the voltage they need and the synth doesn’t properly power up (details of what kind of power supplies I’m using are below). I can mitigate this by plugging the wall warts in one at a time after flipping on the power strip, then usually everything is fine.
Since the power strip and wall warts are all contained inside the rack behind the panels, I want to find a way to avoid having to do that since it will be impossible once the rack is full.
Does this issue sound familiar to anyone? I’m thinking maybe it has something to do with all those big capacitors hogging up “in-rush” current and overloading the power strip, so I’m considering routing the leads from the wall-warts to the eurorack power supplies through some switches on the front panel, and powering up my modular in stages to manage the “in-rush”.
I am a mere hobbyist and by no means an electrical engineer, so if I am off in the weeds, please let me know. If you guys DO think it’s reasonable to power up in stages like that, I have a further question: There are two wires leading from the wall wart AC adapter, to the Eurorack power supply. Should I use a DPDT switch to switch both conductors, or should I try to identify the power wire and switch only that, leaving the ground connected at all times? Will it be necessary to have a fancy heavy duty switch, or can I get by with one of the generic switches I use for signal switching in my modules, such as this? https://www.taydaelectronics.com/mini-toggle-switch-spdt-on-on.html
To eliminate any ambiguity, this is what I’m working with: I have a modular synth with about 22 modules being powered by two power supplies - two of these wall warts:
Into two of these AI Synthesis Eurorack power supplies:
Distribution:
And everything is plugged into one of these power strips:
Thanks a million for any insight you can offer. Have a great weekend!
-Wes
Sounds like a doozy of a problem, and I’d definitely wait for @fredrik, @analogoutput, @ChristianBloch and @Dud to weigh in, but one thing that springs to mind is that I used to have similar problems-albeit not with the same kind of rack-with an old rack mount system. A Furman power conditioner (brand probably isn’t important but I remember that name) seemed to take care of the issues. I don’t know if it’s comparable enough of a situation to be a useful suggestion, but I thought I’d put that out there.
You’ve mentioned one solution, which is not powering everything up at once.
So either you can do this
1: by hand or
2: have some delay circuit (a 555 e.g) switch them on for you. Best then use a solid state relais (and switch the mains side) because that is controlled by an opto coupler which would not draw too much current from the power supply (a relais with a solenoid would).
3: or switch on the first half of the modules directly and have a delay circuit switch on the second half of the modules a few seconds later (e.g. by using a 555 and a small relais).
The other is obvious: get power supplies fitting the power consumption of your rack ( i.e. bigger ones ).
I’d be surprised if the two power supplies I’ve got can’t collectively handle 22 modules, especially given that the distribution boards have plugs for up to 48 modules combined. But I suppose it’s possible I’ve gone over (or approached) the amperage limit.
Indeed, maybe the midimuso is the problematic thing here and I just need to break down and get a dedicated wall wart just for that. I’ll give it a shot and see if that clears up my problems.
Thanks everyone.
-Wes
Just unplugged the midimuso from the eurorack supply and everything started up no problem as soon as I flipped the switch. Seems like that might be the culprit, but I’m really confused by the fact that overdrawing on one power supply would also cause the other to malfunction, even though the only electrical connection between them is at the power strip.
Every time I think I’m starting to understand electronics, some friggin voodoo happens
So it’s what looks like an ATmega328p running at 16 MHz, a couple of level shifters, and three low-power opamps. Seems you’d be able to run that on 25 mA, maybe?
So no LEDs on mine - making it even more mystifying why the vendor recommends 500ma supply minimum. Maybe I haven’t discovered the real cause yet afterall. More experiments to come.
Well, the 500 ma requirement I saw was for the Octex, I can’t find anything about current draw for the ORAC. But your experiment does seem to give cause for concern.
Yeah, that’s the one I was commenting on (the schematics are at the bottom of the page). I cannot see how the circuit itself can pull a lot of current, and even if you’ve connected all the CVs to other devices, that shouldn’t add much. Maybe the regulators are doing weird things (see other thread)?
(the Octex looks like roughly the same but with SMD and many pretty LEDs, but not 475 mA of LEDs unless they’re driving them hard.)
Gah, after some more experimentation it seems I am still having the same issue, even with the midumuso completely disconnected. My current working theory is that the power “conditioner” strip might be tripping some kind of safety mode from the in-rush current, so I’m kinda settled on using switches to start the rack up in stages. That just leaves the one question - can anyone tell me which of these is phase and which is ground? I plan to just slap a switch on the phase, put an indicator LED on a separate circuit and have done with the whole affair.
Thanks for the advice everyone.
I’ll just chip in that ac-ac power bricks and power strips with cheap surge protection can behave in an unpredictable way. Don’t know why. Never bothered to find out, sorry.
That, plus that the transformer cores need to saturate. They can pull a lot of current for the fraction of a cycle they need to do that.
It might be as you say that your strip is trying to protect your gear from itself (not easy to tell exactly what circuitry it has unless you’re willing to take it apart ). The correct solution would be better power distribution on the mains side of things, maybe a beefier strip (more “distribution unit” than “strip”) and limiters (or transformer switch relays etc) on the way out from the unit, so they can deal with the supplies independently, but you need a qualified electrician to get that right.
(I guess moving to a country with 240 V mains is not an immediate option )
(This whole thing is also why I recommend keeping the mains bits outside your gear, btw, beyond maybe a single power cord going directly to a single supply. Those two holes in the wall are happy to kill you if they get the opportunity, or at least set your gear on fire…)
Ok, I’m starting to lean towards my power strip’s cheap surge protection as a possible culprit - do any of you have recommendations for good power conditioners that are up to the task of switching a few beefy ac ac wall warts at once? I’m not sure the rack mount furman power conditioner is going to work for me but Anything with a low profile should be fine. I thought I was getting what I need but I guess not!
Thanks again for sharing info everyone.
-Wes
I really hope that’s an isolated supply (i.e. involving a transformer with no connections between mains and low voltage side). If so, “phase” and “ground” doesn’t really apply downside since nothing’s grounded (the rectifier diodes will sort the phases into the right rail).
You could measure connectivity to be on the really safe side, but Jameco aren’t complete idiots (*), and they have a datasheet on their product page with simplified schematics, which shows that it’s a fuse and a transformer and nothing else; no suspicious connections.
Thanks Frederick. I took a guess that the black-with-white wire was the one I want to switch, and saw that it is connected to the center pin (with the other wire connected to the barrel). Since the barrel is connected to the “ground” points on the eurorack power supply, i plugged it in and gave it a shot on my test power supply.
It seems to work fine, so I plugged it into one of the power supplies in my synth case. It successfully allows my rig to turn on consistently, since now nothing trips on the surge protector (I just wait a few seconds before turning on the second bank of modules). Hopefully this all makes sense and I’m not somehow doing damage to my rig
)
). The correct solution would be better power distribution on the mains side of things, maybe a beefier strip (more “distribution unit” than “strip”) and limiters (or transformer switch relays etc) on the way out from the unit, so they can deal with the supplies independently, but you need a qualified electrician to get that right.
)
