OBERHEIM SYNTH

Scott, There is one on e-bay right now for $20. Both AB and clarostat marketed the identical pots. Problem solved! Search for 

JA1N200P103UA
Auction below. 

http://www.ebay.com/sch/i.html?_trksid=p2047675.m570.l1313.TR0.TRC0&_nkw=JA1N200P103UA&_sacat=0&_from=R40





On Friday, November 22, 2013 1:30 PM, 65 Lotus <Lotus@...> wrote:
 
  
 
Hi James:
 
If you don't mind, where did you find a NOS OB-Xa 
pitch bend pot?  Wouldn't mind having one to return mine to stock 
configuration.
 
And what I really need if anyone has one is a NOS 
Depth pot (just above and to the right of the pitch bend lever). It's got lots 
of problems with the wiper and the push/pull function. 
 
A new one of those and the old girl would be 
100%!
 
Scott
----- Original Message ----- 
>From: James 
>To: oberheim@yahoogroups.com 
>Sent: Friday, November 22, 2013 10:06  AM
>Subject: Re: Re: [oberheim] Oberheim  OBX-a pitch bend issue
>
>
>I  resolved my pitch bend issue. It was just a glitchy pitch bend pot and  cleaning the pot would not clear the dead-band sensitivity.  Sourced a  NOS AB J type 10K and everything is perfect as taper can be slightly different  on the modern replacements. I agree that the pot shaft collar and return  spring mechanism needs to be setup tight but enough clearance to run as  friction free as possible.  Dead band and tuning on both narrow and wide  is spot on.
>
>James
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>On Friday, November 22, 2013 7:09 AM, 65  Lotus <Lotus@...> wrote:
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>And, it helps to tug on the pot shaft slightly  when tightening in order to preload the wiper against the carbon trace. This  got rid of the last little bit of "return to zero" slop in  the new-manufacture replacement pot on my OB-Xa.
>----- Original Message ----- 
>>From: robiecurrier@... 
>>To: oberheim@yahoogroups.com 
>>Sent: Thursday, November 21, 2013 5:01  PM
>>Subject: RE: Re: [oberheim] Oberheim  OBX-a pitch bend issue
>>
>>
>>The slop is really slight and it usually takes me a few tries to get it  perfect. Did you replace the pot or clean it?  If it isn't a new one,  there can be a spot where the carbon is worn away, which would point toward  just replacing the pot.  If the pot is a replacement, the mechanism  that attaches to the pot shaft has to be tightened at the exact right spot,  at least that's how it is on the OBX.  On the OB8, I'd need to look at  the schematic again to know for sure.  It sounds like the issue you are  experiencing will take some experimentation to get right.  Before you  get into that, it would be prudent to replace U2 (1458), D1, and D4 just to  rule them out as causes.  If these don't fix it, then it's probably  wise to check out the mechanicals.  
>>-Rob
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>>
>>---In 
    oberheim@yahoogroups.com, <robhukin@...> wrote:
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>>Hi Rob and All, 
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>>
>>Indeed, I did end up removing the (extra) deadband mod. The existing  deadband circuit works fine as long as U8 is trimmed for 0V. The problem is  that any offset at the NARROW switch (U14) - noticeable by a slight change  in pitch when it is engaged - is trimmed by the CENTRE LEVER trimmer, which  inevitably moves the bender out of the deadband range. I didn’t find a way  out of this problem, but it seemed I was the only one concerned (not the  client). I had stripped, cleaned and relubed the pitch bend pot but I shall  also pay attention the the spring mechanism next time - although there was  no noticeable slop…
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>>rob.
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>>On 19 Nov 2013, at 17:16, robiecurrier@... wrote:
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>>>>I have fixed this issue on multiple Oberheims.  The deadband  mod is not a good solution.  The real problem is mechanical and  oftentimes is two fold.  The first issue is that the sealed pot  used has got carbon powder built up inside on both sides of the wiper.   The pot needs to be opened and cleaned or simply replaced.   This will clean up most of the slop, however, the spring loaded  pitch bender mechanism has two metal arms inside that are attached to a  spring.   These arms are supposed to hold the lever perfectly snug  in the center position, but many times, one arm is slightly bigger than  the other and needs to be filed down slightly where the arm hits the  detent.  You need to shave the arm very slightly so the detent  can't wiggle between the two spring loaded arms.  When you get it  right, there will be no slop and no need for the deadband circuit (which  doesn't actually work properly anyway).  This has solved the  problem in
 100% of the oberheims I have fixed that suffered from the  pitch bender not returning to exact center.  This takes me about 3  or 4 hours to do, and I have done it many times.  I would expect a  first timer to take a couple of hpurs more.  Definitely not a quick  and easy fix, but worth it when done right.  
>>>>-Rob Currier
>>>>
>>>>
>>>>www.NewEnglandAnalog.com
>>>>207-703-2350
>>>>
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>>>>---In oberheim@yahoogroups.com,  <robhukin@...> wrote:
>>>>
>>>>
>>>>Hi All, 
>>>>
>>>>
>>>>I have an OBXa in for repair that has that mod. It is two diodes  (1N914 or similar) in parallel (opposing polarities) connected to the  pot wiper. The wire that was connected to the pot wiper is then  connected to other end of the diodes and this junction also has a 100k  resistor to GND.
>>>>
>>>>
>>>>regards,
>>>>rob.
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>>>>
>>>>On 12 Nov 2013, at 12:27, 65 Lotus <Lotus@...> wrote:
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>>>>>
>>>>>>>>  I  recall seeing a dead band resistor mod for this issue on another  board when using a modern Honeywell/clarostat replacement  pot.
>>>>>> 
>>>>>>That was me. I'll see if I  can find my notes over the next day or so.
>>>>>>
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