[sdiy] Oberheim OB-8

[doof]

Replacing *all* the pots?  That obie must have seen some action in its day
;)

The previous owner of my OB8 had it sitting in storage for several years,
completely untouched which probably accounts for the development of the
scratchiness.  I did disassemble one of the worst offenders and the
resistive material looked perfectly intact- no deep troughs cut by the
wiper.

I really wanted to replace the pots (and perhaps I should have, in
retrospect), but uneveness and stagger on the front panel was of concern and
since the resistive wafers looked intact I decided a cleaning would be the
most effecient route.  I didn't want to use anything harsh like alcohol
since can easily eat away resistive material, and I've heard/read many
horror stories about Caig and pots.  I'm no fan of the overpriced,
understocked shack- but the pot cleaning/lubing solution seems to be very
good.

Of course, mind what Kevin says about not getting it on the PCB, and don't
use too much.  Squirting solution down the shaft is not the way to do it!
The solution will simply drip down spreading over the outside of the pot and
pcb, and what little juice does penetrate the interior of the assembly will
likely carry surface grime and particles in its wake.  Removing the pots and
a short burst into the interior of the assembly would be the safest, that
way the only thing you risk is that component.

Hopefully the switches are a bit easier to find, I have an OB-XA sitting
next to me that doesn't want to go into unison ;)



>    Hi Kevin & list,
>
> > >You know doof, these pots are extremely hard to come by.  Not only
> > >is the spacing of solder pins not found on any currently
> > >manufactured pots, but the shaft-length is also an odd size.  A few
> > >hours of research and you'll come to the same conclusion.
>
>    I'm currently restoring an OB-8 and have to replace literally _every_
> front panel pot on it (it's a sad case, but at least the owner bought it
> dirt cheap!).
>    Anyway, as you say, there are no direct replacements for it, but I
> have found a suitable replacement that involves only a small amount of
> wiring work:
>
>    Page 1064 Digi-Key  P/N: 450D502-7-ND  5K 1" D-Shaft Flat
>
>    Two main issues with this pot:
>
>    1) You'll have to run wires from the solder-eyelets to the PCB
>    2) The D-shaft is backwards to the original so they have to be
>         mounted 180 degrees around.  Good thing you have to do
>         step 1 anyway!
>
>    Otherwise, the shaft length is perfect, just about 1/16" higher than
> the original, which keeps the skirt of the knob just off the panel
surface!
>
>    As Kevin has also mentioned, cleaning old pots isn't necessarily the
> best solution and I will always replace old scratchy pots when I can.
> I've seen some pots where the conductive track has been worn down next to
> nothing and no amount of cleaning will ever bring that back!
>
>    Good luck with the OB-8!
>
>    Tony
>
> -----------------------------------------------------------------------
>          The E-Music DIY Archive - New Site Coming Soon!
> -----------------------------------------------------------------------
>
> "We wouldn't want to ship something that doesn't work"
>    - Carl Stork, general manager, Microsoft Windows division
>      Excerpt from EE Times April 2, 2001
>