Xref: utzoo sci.electronics:3903 rec.music.synth:4673
Path: utzoo!attcan!uunet!husc6!rutgers!tut.cis.ohio-state.edu!osu-cis!att!ihlpa!rwn
From: rwn@ihlpa.ATT.COM (Bob Neumann)
Newsgroups: sci.electronics,rec.music.synth
Subject: Re: TROUBLESOME OB-X
Summary: some suggestions
Message-ID: <9575@ihlpa.ATT.COM>
Date: 23 Sep 88 18:10:36 GMT
References: <1842@erix.ericsson.se>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 38

In article <1842@erix.ericsson.se>, etxbrfa@kklm01.ericsson.se (Bjoern Fahller) writes:
> Not very long ago, I bought a second hand Oberheim OB-X. I got it quite
> cheap, because it sounded quite pourly. I didn't think of that as a problem,
> because an electronics engineer should be able to fix such things. 
> Unfortunately, it was much worse than I expected.
> A few days later it was quite tuned though, but the filters were impossible
> to tune to my ears satisfaction. The AUTO button, which I think is an auto
> tuner, does not have the desired effect. Pressing the AUTO button, is the
> absolutely best way of getting the synth detuned (and impossible to tune
> again, unless powered down).

I used to own an OB-Xa, which used the same circuitry as the OB-X
except for some software changes that allowed for splitting
and doubling of the keyboard.  The OB-X and OB-Xa voice cards
did go out of tune due to age, and are frequently in need of repair.
I got rid of my OB-Xa in favor of an OB-8 which had better, more
reliable voice card architecture, but the sound just was not the same
as the OB-Xa.  I also have an Xpander now, but that's another story...

Anyway, I would suggest taking the synth in for some service if you
do not want to do the servicing yourself.  I believe one of the problems
with my OB-Xa was unreliable tuning pots, and they were all replaced
under warranty. This vastly improved the tuning problem.

On my OB-Xa, there was a dip switch located inside the instrument on the
inside of the top panel towards the "rear" of the instrument (where the
output jacks are located).  Flipping these switches "turned off"
the voice cards so they could not be used by the keyboard.
Turning off only the switches related to the offending voice cards
enables you to use the stable voice cards in a 2, 4, or six voice 
configuration.

Check to see if a dip switch like this exists in your instrument.
It may help you until the other voice cards can be fixed.

Bob Neumann
PO BOX 1582
Bridgeview, Ill 60455 USA