[FIXED] OB6 broke? Need some verification

I need guidance/help to verify something. I believe the square oscilator of OSC2 is broken.

On my OB6, init patch, I turn down volume for OSC1, turn up volume for OSC2, I now hear OSC2.

If I turn the OSC waveform knob to the right, where it’s square wave only, silence. No amount of changing the pulse width or anything else brings is to life. That’s not how it’s supposed to be. I wonder if I’m overlooking something.

Trying to use that OSC2 square wave as modulation with the X-mod also doesn’t produce anything. If I turn the knob to other waveforms, it does.

Could it be that only the square wave broke? I have no idea how it’s working internally, is it a chip per waveform?

Turn the osc2 Pulse width to noon :wink:


I know that, and it is, it’s with the INIT patch.

But thanks :wink:

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I’d eliminate the pulse width by changing it via midi cc if you haven’t already done that, might be the PW control that’s bollocksed.

Long shot, but it at least eliminates one potential issue.

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Thanks for the tip. That’s cleared, just did that, still nothing. Actually, not nothing, there’s a tiny noisy signal. I tried the Unisson with 6 voices to see, and same.

Which makes me wonder. I’m an ass with electronics, but I’m quite sure there’s one chip per voice for producing sound, must be something else that broke.

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To confirm, with anyone that has an OB6, you got sound when doint that right?

  1. Load INIT patch (MANUAL + WRITE)
  2. Turn down volume of OSC1
  3. Turn up volume of OSC 3
  4. Turn waveform knob of OSC2 to the far right, to the Squarewave postion

Do the knobs transmit midi?

If they do see what the PW knob is transmitting.

I can’t help but feel something is up with the PW.


Sounds like something’s wrong. Contact sequential customer support, they’re fantastic.

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I read PWM sorry.
Same as @Fin25, feels like Pulse Width is the obvious culprit one way or another.
Unplug MIDI and play a sequence from the synth and tweak.


Was having the same feeling, unfortunately it doesn’t seem so. The knob is transmitting CC data (could record it). I tried to send it data through CC as well.

I mean, it could be that PW is broken and not the OSC, indeed, but not the knob nor connection to MIDI. Maybe the actual PW electronic component (I’m REALLY an ass with that :slight_smile: )

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I did, indeed. Thanks.

It’s a module so I need MIDI to play it. But I tried with a sequence from Ableton Live, as well as just a MIDI keyboard, same.

PW broken, I guess. Damn! It’s still has a few months of warranty luckily. I’ll be sad to not have it, even for the time it takes to repair…

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No: set the MIDI clock to OFF or OUT, and hit play to hear the sequence without MIDI input.
Then tweak your OSC2 PW pot :slight_smile:
And tell me it’s all good.

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Ah, the sequencer, but of course.

I turned off MIDI clock, unplugged both USB and MIDI cables, played a sequence and… no joy :disappointed_relieved:

Thanks for the suggestion though!

Damn. :pleading_face:

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Stupid question but the mod wheel is down right?

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Ain’t no mod wheel on the module. And external MIDI has been ruled out.

@amaury could you drop a picture of the synth, just in case?

You mean, to see the knob positions?

If so, 'm starting from INIT patch, the knobs aren’t where the parameters are. I could “reset” all knobs but it seems futile. I moved the relevant ones. Unless there’s another parameter that could cause OSC2 square wave to be silent, besides its PW…

@amaury what do you call “INIT patch” exactly?
I thought you were in Manual mode: best way for ruling out unseen problems is to switch to this mode and hear what you see. :nerd_face:

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So I’m no pro but it sounds like you might need to open it up. Some possibilities as you might guess are:

  1. the audio connection is out (check with multimeter, solder the broken connection to fix)
  2. the square wave is probably driven by some kind of clocking IC, and that’s dead (step 1 fails to turn anything up, to fix replace bad components).

Here 2 could optionally be just about anything (bad capacitor, etc.) so that’s where a pro would be a nice touch instead of replacing everything in that circuit.

Hope this gets you started.

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