[sdiy] Oberheim OB-XA autotune procedure questions

[Kevin Lightner]

>Hi all,
>
>I've just finished replacing the battery in my OB-XA (along with 
>installing new bushings and cleaning some problematic J-wires) and 
>I've found that all voices now fail the autotune procedure.  When I 
>press the button, it cycles through all 8 voices, then the 8 LEDs 
>flash for about 2 seconds.  All 8 voice cards are perfectly 
>functional.
>
>I have both versions of the service manual, and neither address the 
>autotune function other than using it in calibration routines.  How 
>autotuning is implemented and any specific 
>troubleshooting/calibration strategies are completely neglected.
>
>So I'm wondering what could possibly be contributing to this 
>problem.  Autotune worked before the battery replacement, although 
>tuning wasn't perfect.  Does something within the circuit rely on 
>battery power to retain memory for the autotune algorithm? 
>
>At first I thought bad tuning might be causing the problem.  Turning 
>the voice disable feature off with the test2 switch, I've started 
>calibrating the individual voice boards to achieve better tuning, 
>yet reagardless of the more accurate initial tuning the autotune 
>function still does not want to cooperate.
>
>Looking back at the AH archives, it seems a few people have 
>experienced this exact problem, though no answer ever surfaced. 
>
>...Anyone?
>
>Thanks.


Any time one works on something vintage, strain is placed on solder 
connections, connectors, etc.
Very likely you inadvertently moved something and it caused this.

Generally the biggest problem I see with people attempting their own 
work on vintage synths or anything else (and no slam personally) is 
assuming that what they know is all they'll need. It's *always* what 
you don't know that will bite you. With that said, I'd recommend 
going over your work carefully and inspecting everything closely 
under bright light. Power supply solder connections are notorious for 
being bad on OB-Xas, along with their connector pins. I won't work on 
one without flipping that board to see what's up even before I power 
it up.

-- 
Regards,
Kevin Lightner

http://www.synthfool.com
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