Page 1 of 1

ARP odyssey

Posted: Wed Mar 04, 2009 6:21 pm
by michael stein
My friend has an MKII odyssey with a problem. When a key is pressed the gate signal somehow causes the oscillators pitch to change and when the key is released the pitch changes again, the oscillators seem super drifty. The only way you can play it is to turn the release off completely and then your stuck with this semi portamento effect at the attack of the note. And then its stil impossible to tune. Any idea......?????
Thanks

Re: ARP odyssey

Posted: Wed Mar 04, 2009 7:00 pm
by cornutt
Sounds like something is wrong with the sample-and-hold circuit that grabs the keyboard CV and holds it when a key is pressed. Sometimes, on an old synth, the circuit board around the S/H circuit's holding capacitor gets dirty, and it bleeds the charge off the cap when the gate closes. So the first step would be to locate the keyboard S/H and give that part of the board a good cleaning. Beyond that, it may be a faulty cap, or there may be something wrong with the op-amp that the charge holding cap is connected to. I'm not an Odyssey guru, so I can't be any more help than this.

Re: ARP odyssey

Posted: Wed Mar 04, 2009 7:11 pm
by Synthaholic
Maybe the key contacts are dirty.

Do both oscillators exhibit the same symptoms? The Odyssey is duophonic, so that would mean the keyboard generates two CVs, there are two S&H circuits, etc.

Re: ARP odyssey

Posted: Wed Mar 04, 2009 7:34 pm
by michael stein
I will have to check on that cornutt. This is a great start. Thanks duudes.

Re: ARP odyssey

Posted: Wed Mar 04, 2009 9:10 pm
by meatballfulton
Tuning problems may be nothing more than dirty tuning sliders. I had that issue with my Odyssey, when I opened it up there were hairballs on all the sliders. I cleaned them out and then the pitch drift was gone.