Vintage Synth Repair

Will anyone with some familiarity with the Roland Sys 100 Model 101
noise circuit (or comparable discrete design) please give a brief
explanation of the circuit and how it functions?  It doesn't appear to
incorporate any IC's.  I'm attempting a repair.  These older synth
boards are a little harder to trace and troubleshoot for me.  The
basic symptom is that the noise slider, when maxed, maintains a low
noise output volume or, when zeroed, still outputs some noise (though
slightly quieter than the maxed scenario).  Thanks! --Stephen