[sdiy] Oberheim FVS calibration

[Maarten]

Hello Al,

I don't have an Oberheim calibration procedure but I can share the way I 
calibrate the key assigner and the programmer overhead board.  The 
numbers of the trimmers might not correspond with the Oberheim numbers.

Keyboard assigner

/Keyboard Assigner/

Use T3 to obtain + and – the same voltage. (Balance) Single turn trimpot
Set keyboard assigner to unison, no split, portamento off.
Connect voltage meter to CV out channel 4 on backside. Measure offset 
when lowest C(C1) key is pressed. Adjust T2 for exactly 4.000V 
difference between lowest C and highest C(C5). Verify keyboard voltage 
for C2, C3 and C4. Measure the voltage between Connector L1 en L2 . 
Adjust T1 for exactly 1.000V differencebetween octave switch centered 
and octave switch up. Verify down is -1.000V difference.
Portamento, check if all voices have the same portamento time when 
portamento is at max. Trimmers are located on the polyphonic keyb 
channel logic board (1103D).

/Programmer overhead board/

Adjust T1 for +15.000 Volt on connector T5 and T6.
Adjust T2 for 10uS A11 pin 13.
Adjust T3 for 10.000V on N1 (My notes also mention 10.350Volts, I am not 
sure about this)

Best regards,
Maarten


Op 18-3-2025 om 01:21 schreef al spitzley via Synth-diy:
> Hello all,
> I’m trying to calibrate an 8 voice and want to make sure I’m doing it 
> in the correct order. My main issue is when/how exactly the programmer 
> DAC should be calibrated. I’ve been doing the sems then tuning the 
> programmer boards to each other but I’m not sure if this is the 
> correct order to do it. I have not found any instructions on the web 
> for the programmer or the assigner boards.
> Any help greatly appreciated!
> Thanks
> Al
>
>
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