Korg Mono/Poly

Hi,

I got a mp4 that I recently  recalibrated and is working very nicely. Tuning/scaling is very good.
I checked all the voltage and got good and steady readings on the power supply and keyboard CV voltages.

But when it comes to measure the VCO offset in the klm398 I don't get the 0.000v +/- 1mv. Instead I read voltages bretween 1v and 3v and they change if I play notes on the keyboard. The voltages are responsive to the different VR on the board but I can't make them 0.000v.

So question are:
- Am I reading the good points ? i connected to J12 and to the respective 4 colour wires mentionned in the manual (and corrected here for new version)
- Is there a key to press while reading ?
- Is it dangerous for the OSC to have these readings ? As i mentionned my mp4 is really nice tuned and scaled, for every oscillators.

Am 29.10.2012 01:53, schrieb ohmstudiste:
> Hi,
>
> I got a mp4 that I recently  recalibrated and is working very nicely. Tuning/scaling is very good.
> I checked all the voltage and got good and steady readings on the power supply and keyboard CV voltages.
>
> But when it comes to measure the VCO offset in the klm398 I don't get the 0.000v +/- 1mv. Instead I read voltages bretween 1v and 3v and they change if I play notes on the keyboard. The voltages are responsive to the different VR on the board but I can't make them 0.000v.
>
> So question are:
> - Am I reading the good points ? i connected to J12 and to the respective 4 colour wires mentionned in the manual (and corrected here for new version)
> - Is there a key to press while reading ?
> - Is it dangerous for the OSC to have these readings ? As i mentionned my mp4 is really nice tuned and scaled, for every oscillators.

Others may correct me, but I think you misunderstood the adjustment 
description: As far as I understand it right this is not a trimming to 
absolute 0.000V +/- 1mV, but the voltages should not vary more than 1mV 
in relation to each other.

Florian
-- 
http://fa.utfs.org/

I went through this when I rebuilt my trainwreck Mono/Poly. The offset is obviously only a part of the overall procedure but it was a case of adjusting to get as close to zero as possible but measured at pins 1,3,5&7 on connector 39. The whole procedure I used is in the forum 'Files' section under 'Misc Files' - 'Poly.pdf'.
Good luck
Steve

--- In korg_mono-poly@yahoogroups.com, "ohmstudiste" <ohmstudist@...> wrote:

>
> Hi,
> 
> I got a mp4 that I recently  recalibrated and is working very nicely. Tuning/scaling is very good.
> I checked all the voltage and got good and steady readings on the power supply and keyboard CV voltages.
> 
> But when it comes to measure the VCO offset in the klm398 I don't get the 0.000v +/- 1mv. Instead I read voltages bretween 1v and 3v and they change if I play notes on the keyboard. The voltages are responsive to the different VR on the board but I can't make them 0.000v.
> 
> So question are:
> - Am I reading the good points ? i connected to J12 and to the respective 4 colour wires mentionned in the manual (and corrected here for new version)
> - Is there a key to press while reading ?
> - Is it dangerous for the OSC to have these readings ? As i mentionned my mp4 is really nice tuned and scaled, for every oscillators.
>

Oh stupid of me !
Than it makes sense of course. And now I managed to adjust them correctly (there was a 0.05v drift).

> Others may correct me, but I think you misunderstood the adjustment 
> description: As far as I understand it right this is not a trimming to 
> absolute 0.000V +/- 1mV, but the voltages should not vary more than 1mV 
> in relation to each other.
> 
> Florian
> -- 
> http://fa.utfs.org/
>