Vintage Synth Repair

Hi guys, just calibrated my Jupiter 4 using the service data and a
scope..well it all sounds great now except for the preset 'Voice'
sound, it's very quiet. All the other presets are nicely balanced and
sound correct except for this one's level. I've been back through my
calibrations 3 times over and everything looks perfect. Anyone know
anything about this?

Also I have a click at the start of one of the notes, I've traced it
down to one of the module boards..and looking at the schems it looks
like IC16 a Roland custom BA662 is the culprit. Is there a source for
these anywhere? UK preferably..Also I've read conflicting information
about the BA6110 being a suitable replacement..can't find a definitive
answer though.. again any info would be helpful.

Thanks, Phil.