A Eurorack DIY project that took some creative thinking about its packaging, this Jupiter Storm Cosmic Noise Oscillator by HEXINVERTER came as a panel/PCB from Modular Addict.
Whoa, the DIY PCB is wider than the panel! After meditating on how to mount the module in a case, I finally decided to commit my smaller 4ms Pod to Jupiter Storm. It fits quite well, with plenty of elbow and headroom.
PCB assembly
Besides the BOM, Modular Addict links a Mouser project cart. I copied and modified it, as I already had many of the parts on hand. The toggle switches listed in the Mouser project were different from the part given in a note in the BOM. I snagged a pair of the ones from the note, as they are specified as M5 diameter rather than M6. I did not have to drill the panel at all.
I traced the circuit so I could understand it better. By design the Oscillator 1 output is affected by the feedback switch, a.k.a. the Noise Core Disruptor. I preferred this not to happen, so I made one wiring change. That’s the gray jumper wire.
Panel Wiring
The build guide contains a useful pictorial of the panel wiring. It’s straightforward. Step one was to prepare all the wires and solder them to the PCB. Step two was to wire them to the panel. I used my PCB holder to keep the board in place over the pod during wiring.
THIS DIY MODULE HAS NO WARRANTY OR SUPPORT.
IT WAS BUILT BY A FELINE HIGH ON CATNIP.
So says Hexinverter!
Finished
Four passive attenuators for reducing CV inputs and two active mixers for mixing outputs accompany the Jupiter Storm. FM cross-modulation will be easy.
Testing
As seen above, the oscillator square waves are crisp and swing about 12 volts P-P. All the outputs are capacitor-coupled.
The frequency ranges go from sub-audio up to 16.7 KHz. I found that the lowest frequency of each oscillator varied quite a bit: 11 seconds, 7 seconds, and 2 seconds for oscillators 1, 2, and 3. The middle setting on the pots resulted in 560 Hz, 730 Hz, and 640 Hz, respectively. The high was 16.7 KHz for all of them. All three oscillator circuits are identical, so I can’t account for the differences, but it may be due to using non-matched transistors in the exponential converters.
Due to capacitive coupling, the outputs skew at LFO frequencies. Such frequencies are probably best put to use when combining oscillators for the main outputs. Also for FM of the other oscillators.
Just oscillators 1 & 2 XOR’ed together are available at output I. Outputs IV, VIII, and XI are subdivisions of this by 4, 8, and 11, respectively. Turning on Oscillator 3 XORs it into this output as well.
I just finished my Jupiter Storm build and ran into trouble. At first, the oscillator outputs were working as expected, but nothing from the other bottom outputs. Then i tried patching oscillators into a fresh build of Manhattan Mix (previously untested) and nothing. Then i tried just the JS oscillator outs again and nothing. A strange chemical burning smell was observed and my power supply indicator LED stopped working. I tested the power supply rails and was reading -.7v at the positive end and about -5v at the negative. Other modules on same power supply not working either now. Supply is an MFOS bipolar. I’m not very skilled / experienced with troubleshooting, so I don’t know where to start. Thanks in advance.
Here are some things to do.
Unplug all modules from the power supply and test that it is reading +12V and -12V. If not, you’ll need to fix or replace the power supply.
One at a time, power each good module and test that it’s working.
On the Jupiter Storm measure the resistance at the power connector between +12V and ground, between -12V and ground, and between +12V and -12V. Should be well above 1K.
Look (and smell) for any burned parts on the Jupiter Storm. Replace any found. Repeat resistance checks and try again.
Thanks.
Have determined that the JS somehow fried my MFOS bipolar supply (which is linear, as the JS build guide recommends).
The supply definitely had a bad smell and the +V regulator was hot all modules removed, giving the same power readings as before (-0.7v at positive and -5v at negative).
Nothing looks or smells burned on the JS.
Was thinking to maybe try powering the module with batteries, but don’t want to blow them up.
So, w/o power, took resistance readings at the points you suggested.
Ground to +V began reading close to 0 ohm and climbed up until about 1.9M. The increase in resistance started climbing quickly and then much slower the higher it got (as in several minutes).
Ground to -V read 0.
-V to +V read 34.3k.
Thanks so much for your help, Richard!
Richard, this build and explanation was extremely useful to me as I am trying to troubleshoot a broken one of these, but it’s the smaller smd version built from the factory – everything works except the last three outputs (IV, VIII, and IX) – as you explain these as subdivisions of Output I, which works fine, is there an IC you would expect to be the culprit to knock out these subdivisions? Which IC is responsible for those divisions?! Thanks, as I said, this article was super helpful already!
Hi Ryan,
The CD4040 is the divider chip. The BOM says to use Texas Instruments chips. Did you? I always use T.I. for CMOS.
Thanks Richard! I didn’t build this one, just repairing it, but I will check voltages at the 4040!