Vintage Synth Repair

Hi guys

okay after three long years, I finally have had a chance to work on my 3200... it is working 100% except for one annoying problem.  I am hoping that someone out there might have an idea what is happening with this beast.. below is a description of the problem as well as a list of things we have tried to repair the problem.

the problem:  

the 3200 is working 100% except  there is an issue with the recall of memory.  the problem is centered only around the Signal Generator Waveforms ( most noticeably present in the pulse and square wave forms) after the patch is saved the recalled patch has a constant 5-7Hz square wave vibrato that is present on all notes unless the SG 1/2 waveform knobs are pulled (bypassing the memory).. we have been unable to find the source of the Vibrato .. it is not the Modulation generators or Ensemble oscillator

notes:

- keyboard pitch doesn't effect the vibrato rate
- DAC Gain Pot has no effect
- ADC Gain pot has no effect
- Memory Master Clock Freq/Duty cycle pots have no effect
- All Memory ICs were swapped and problem still is the same
- Changed all MUX and DMUX ICs and problem is still present
- PSU voltages all Ok and clean
- DAC IC changed and problem is still present

the last IC I have not changed is the teledyne 5000CJ ADC I have sourced the part but it costs over $150 with the shipping etc... this may be the problem but I am hoping to rule out anything else that we are not considering before I dish out the $$.

any one have any ideas?  any help is appreciated

thanks

-rick



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