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cactusleaf

Arp Odyssey oscillator mystery

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Ok, so I got an Arp Odyssey on eBay, and it came today. It's really amazing.

 

It has a large problem though, namely: oscillator 1 doesn't respond to the keyboard or the octave switch. It does work, and it responds to the tuning sliders and its various other modulation sliders (S/H, ASDR, etc.) just fine. Osc 2 is fine and everything else (except pink noise) is great too, if not a bit touchy. Osc 1 just isn't playable.

 

Before I take it to a tech, has anyone seen this problem before? Any revelatory advice? Thanks big time.

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This may or may not help. The Arp Solus/Odyssey default to a static pitch(c1?)same with the keys when the CV in are engaged.I wonder if osc1(everything actually) will respond to midi/cv in the correct fashion,and/or is it stuck in CV mode.I have no idea why 1 osc would do this by itself,but it might be good to try and see..just a thought.

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I don't know, but I picked up an Arp Solus not long ago and Osc1 wasn't working at all. In the process of troubleshooting, I somehow killed Osc2 too! I'm gonna jump back into it soon.

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My best bet would be that there's a problem with the buss-bar that the key contacts touch to make pitch. Depending on the model there may be a plastic plate screwed to the bottom of the Odyssey held in place by 6 tex screws. Remove the plate and you should see the buss bars. Check to see if the wire is securely soldered to both bars. If so, remove the 2 screws on either side of the keyboard and lift the control panel. Follow the wires from the bus-bars and see if they're securely soldered into the citcuit board. IF so, check voltage between the 2 bars and ground and see if they match. I believe it's supposed to be 15v. but it's been a while since I measured it.

 

Oh yeah, one other thing. If one of the key contacts (J-wires) are bent or wrapped under the buss bar (making permanent contact) it can't re-gate the oscillator to start a new note. If you see a j-wire making permanent contact with a buss bar, gently bend it from underneath the buss bar so that it sits aproximately 1/8" above the bar with the keys at rest.

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The Odyssey is duophonic meaning there are two control voltages generated by the keyboard, one for each oscillator. I suggest following jchas's advice and check the bus bars for proper connections/voltage.

 

I don't know if the Odyssey has the ability to disconnect the oscillator's pitch from the keyboard like some synths like the Pro-One has. Check all the switches/controls, maybe one of them does this.

 

You say the ADSR works fine, so that means the gate signal is ok. Just the keyboard pitch CV for osc 1. is the problem.

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One more thing. If you don't have a plastic cover on the bottom of your machine you will need to remove the control panel as I mentioned above (be carefull - the Odyssey uses multi-pin connectors and the wires aren't very long. You may unplug something as you lift it up). Once the panel is off you will need to remove a few screw that mount the keyboard to the chassis to access the buss bars underneath. Good luck.

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kpatz had a very good point, one that I thought would be a no-brainer - but since you're brand new to the Odyssey...

Have you checked the switch just to the right of the tuning sliders for OSC1?

It's marked KYBD-ON / KYBD-OFF. It could be in the wrong position or dirty. It should fairly easy to jump it with a test lead once you have the control panel removed.

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Slide switches are notorious for getting dirty contacts as they age. Toggle them back and forth to scrape the gunk off the contacts.

 

The keyboard buss is not the problem if OSC2 is tracking the keyboard.

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The keyboard buss is not the problem if OSC2 is tracking the keyboard.

AFAIK the Oddy has 2 bus bars in its keyboard, one for each oscillator. Unless they did the duophonic thing some other way...

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They have three busses - trigger, gate, and keyboard CV. Some models omit the third buss and trigger is derived using combination of gate and keyboard CV.

 

The duophony is done using voltage differential sensing between two pressed keys in the keyboard resistor string on the keyboard CV buss.

 

If one VCO tracks but the other doesn't, the buss is not the problem. The buss is common to both VCOs.

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On 3/6/2008 at 8:33 AM, jchas said:

My best bet would be that there's a problem with the buss-bar that the key contacts touch to make pitch. Depending on the model there may be a plastic plate screwed to the bottom of the Odyssey held in place by 6 tex screws. Remove the plate and you should see the buss bars. Check to see if the wire is securely soldered to both bars. If so, remove the 2 screws on either side of the keyboard and lift the control panel. Follow the wires from the bus-bars and see if they're securely soldered into the citcuit board. IF so, check voltage between the 2 bars and ground and see if they match. I believe it's supposed to be 15v. but it's been a while since I measured it.

 

Oh yeah, one other thing. If one of the key contacts (J-wires) are bent or wrapped under the buss bar (making permanent contact) it can't re-gate the oscillator to start a new note. If you see a j-wire making permanent contact with a buss bar, gently bend it from underneath the buss bar so that it sits aproximately 1/8" above the bar with the keys at rest.

Hi - 

Resurrecting an old thread. 

I just picked up an old Odyssey for cheap.  I'm having an issue all keys are producing the same pitch. I measured (2buss model) the CV Buss is showing -.08 V when no key pressed, and raises to 0 when ANY key is pressed.  (Gate CV is fine)  My understanding is that it should go from 0-3V depending on which key is pressed, 1v/OCT.  The keyboard high and low is showing 3V across them appropriately.   Everything looks well connected, I'm wondering if the resistors could be shot for some reason but seem unlikely all resistors would ALL fail? 

Thanks for any thoughts. 

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