Vintage Synth Repair

On Friday 18 April 2008 10:43, eggwheatis wrote:
> 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.

I don't think that's a "Roland custom" part,  I believe that it's probably 
made by Rohm.  I don't seem to have a datasheet on it yet,  though.  There 
seems to be some info on it here:

http://www.synthdiy.com/show/?id=2270

According to the info on that page there might be an issue with DC offset, and 
the pinout given doesn't seem to show any offset adjustment pins.  If there's 
a "balance" or similar adjustment n the module board that's givnig you the 
click try that and see if it gets you anywhere,  if there isn't one there it 
should be possible to add one without too much trouble.

> Is there a source for these anywhere? UK preferably.

I'm not seeing anything in my searches so far except for one place that 
claimed they could get them but has a $75 miniumum order per line item.

> .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. 

I believe the link above also touches on that,  too.  I do have a datasheet 
available for at least one version of the BA6110,  to be found through 
http://www.classiccmp.org/rtellason/parts-index.html with the exact part 
number for what I have being BA6110FS (I assume that the FS applies to case 
style, maybe).

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin