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Troubleshooting an issue w Rubicon, O_C, and MN Skiff
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Troubleshooting an issue w Rubicon, O_C, and MN Skiff
Pyrrhix
I'm brand new to modular, but not new to synths. I'm having an issue that appears to be power related with my newly-bought second-hand Rubicon, O_C, and Make Noise Skiff. Here's the issue:

When I have the O_C and Rubicon hooked up to the skiff, the Rubicon behaves erratically; the PW knob spits out heinous noise at various points of the knob travel, and square waves come out of the other waveform outputs. When the O_C is not hooked up, the Rubicon does just fine, and the PW knob gives me normal PWM for its entire travel. My other modules appear to be unaffected by the O_C's presence, and the power adapter is plenty powerful to power all modules present.

I'm not sure what to make of this. I can move the O_C to my impending second skiff, but I don't want to end up with the same issue again with another module. Is the Rubicon especially sensitive to power fluctuations caused by a digital module? Is the power board or adapter not working properly? Is the O_C a jerk? What gives?
Timmy
Is the O_C module behaving correctly, producing correct voltages on all outputs etc? If not, there may be a fault in it's construction (did you build it yourself or buy it ready-made?), such as a short somewhere which is causing serious voltage droop on your power rails. In general, the O_C design is not a jerk, but your particular O_C module may well be.

Also, are you sure that you have enough power for your skiff? What power draw does ModularGrid estimate on each rail, and what power supply are you using?
thomachine
Is it just the PW knob on the Rubicon that is acting up? I have both the OC and Rubicon in my case. Powered by a Doepfer PSU2, and havent noticed any problems yet. But i havent tried the PW knob after i got the OC.
BaloErets
Curious as to which version of the skiff you have.

Is the board inside quite small taking up about 20% of the skiff or is it rather a longer board that takes up most of the skiff?

For the record, I have both modules in the latter and they behave without issue. I do have the other Skiff as well. Could always pull it out to see how they behave if that’s the one you have.
Trebbers
This is a thing that comes up w/Rubicon and digital modules.

https://forum.intellijel.com/t/rubicon-problem/405/2?u=trebbers
Quote:
I had v. similar symptoms with my Rubicon. Turned out to be an issue with digital modules pulling a large amount of current when powered on. I was also well within the limits of my power supply, but (I’m assuming) the Rubicon was starved on startup and didn’t like it. Put most of my digital stuff on a different PSU and the Rubicon was fine.
Pyrrhix
Sorry for the delay in responding here.

First off, thanks to everyone who chimed in with helpful info. I think I have gotten to the bottom of this issue, so I wanted to post back in case anyone has a similar issue in the future.

I got a second MN Skiff. It came with a different power adapter that actually has a Make Noise sticker on it. I'm not sure if the first Skiff came with an aftermarket adapter or if it's the adapter they previously came with. The second Skiff was made in 2017, the first one was made in 2015. Both have the power board that spans the majority of the case.

I tried powering O_C and Rubicon in both skiffs with the new MN adapter and the Rubicon worked fine. So, the issue appears to be with the first adapter. But, the first adapter is properly rated to power the skiff, and no other modules exhibited issues with that adapter.

As Trebbers pointed out, other people have had issues with the Rubicon acting up in the presence of digital modules. Yet, thomachine has been using both modules together without issue.

My conclusion with my limited Eurorack/power knowledge:
It seems that the Rubicon is indeed sensitive to the presence of digital modules and power that is compromised in any way. When just the sub-par power adapter was present, there was no issue. When the sub-par power and O_C were present, the issue emerged. But, with the better power adapter and the O_C, everything worked fine. So, if you are having problems with odd behavior from the Rubicon, the issue may lie with your power supply or adapter.
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