Vintage Synth Repair

Hi everybody,

I'm trying to fix an white ARP Odyssey 2800 but I'm having a hard time.
The problem is that the octaves on VCO-1  are not linear. For example, if I play a low C on the keyboard the next C  will be an A. 
I made the adjustments like described in the service manual but I not able to get the octaves in tune.
I replaced the capacitors in the VCO-1 circuit. It improved a little bit the linearity of the octaves but I'm still not able to tune it properly.
Does anybody have some suggestions to fix this problem? 
Thank you!

Nicolas

Is VCO-2 tracking properly? If so you can compare the two and look for where the voltages do not match.

-Alex

--- In vintagesynthrepair@yahoogroups.com, "Nicolas" <nico678@...> wrote:

>
> Hi everybody,
> 
> I'm trying to fix an white ARP Odyssey 2800 but I'm having a hard time.
> The problem is that the octaves on VCO-1  are not linear. For example, if I play a low C on the keyboard the next C  will be an A. 
> I made the adjustments like described in the service manual but I not able to get the octaves in tune.
> I replaced the capacitors in the VCO-1 circuit. It improved a little bit the linearity of the octaves but I'm still not able to tune it properly.
> Does anybody have some suggestions to fix this problem? 
> Thank you!
> 
> Nicolas
>

Caveat: I am not a tech.
But I can't help but ask--did you replace the trimmers as well?

Hi,

The trimmers are fine.
When I'm comparing the voltages beetwen VCO1 and VCO2, the pitch of VCO1 is shifting if I touch the grid of its JFET (Q6) with my voltmeter probe while there is no effect on VCO2 if I touch the grid of its JFET (Q13).


Nicolas

--- In vintagesynthrepair@yahoogroups.com, "Monie" <arp2600fan@...> wrote:

>
> Caveat: I am not a tech.
> But I can't help but ask--did you replace the trimmers as well?
>