Vintage Synth Repair

Been a couple of years since I did an OBXa.  One of the ways to work on issues related to a CPU that will not run is to ground the data bus of the CPU.  This will cause the address bus to auto increment, and with an o-scope, one can do a lot.  As I recall , there is a slide switch that will do this.  There is also a switch to engage the calibration routine.  

Do you have the calibration document?  As I recall it talks about the no-op too.







>________________________________
> From: Thomas Heckmann <troperecordings@...>
>To: vintagesynthrepair@yahoogroups.com 
>Sent: Wednesday, December 5, 2012 4:32 AM
>Subject: Re: [vintagesynthrepair] OBXa diagnostic EPROM needed
> 
>
>  
>HI,
>it's powering up, but just a few LEDs are on and no sound or response from the keys to the voiceboards.
>The Z80 is fine, too.
>Thanks,
>Thomas
>
>
>On Dec 5, 2012, at 1:27 PM, Roger J wrote:
>
>  
>
>
>What are the issues that you are trying to correct?  There are built in aids like calibration and no op.  
>
>
>
>
>>________________________________
>> From: Thomas <troperecordings@...>
>>To: vintagesynthrepair@yahoogroups.com 
>>Sent: Wednesday, December 5, 2012 3:51 AM
>>Subject: [vintagesynthrepair] OBXa diagnostic EPROM needed
>> 
>>
>>  
>>Hi guys,
>>
>>thanks for approving my membership to this list :-)
>>
>>I'm restoring an Oberheim OBXa 8-voice and looking for the diagnostic EPROM with paperworks for it. A BIN would be fine.
>>It's REV C mainboards and has a Numera Midi interface installed.
>>Will probably remove the Numera first to get the machine up and running and see if it's the Numera that's causing trouble.
>>Fortunately all the voiceboards are fine.
>>Any help would be great and appreciated :-)
>>
>>Best regards,
>>
>>Thomas
>>
>>
>>
>>
>
>
>
>Thomas P. Heckmann
>Trope Recordings - AFU Limited - AFULAB - trope mastering
>
>
>
>
>
> 
>
>