Casio CZ/ VZ/ FZ - Pro Series

>If we can just figure out what part of the synth needs to keep that
>voltage running through it, we can just find the +voltage / -voltage
>ports and maybe just solder on a 3V lithium watch-battery cell, like
>on the Korg Poly 800.

It's not as straight-forward as it sounds.  Obviously power needs to be 
continuously supplied to the RAM chips.  And there's at least some provision 
for this, as the synth retains patches when switched off- but simply 
connecting a battery across the RAM power supply lines isn't a good idea.  
When the synth is powered up, the backup battery would then be connected 
directly across the power supply, which will possibly make the battery 
explode.  I think you could connect a diode so that power only flows from 
the battery when RAM supply voltage drops below battery voltage, BUT with 
the resultant voltage drop (about 0.7 volts), it may not be enough to hold 
the RAM contents.  You could probably find the RAM chip's datasheet and 
check.  I'm not sure how memory retaining circuits generally work, maybe the 
best approach would be to analyze the schematics of another device for 
inspiration.

An alternative would be to connect a super capacitor to the RAM power supply 
lines.  These are typically used in things like VCRs, etc. to save settings 
and things during short-term power loss.  I think the installation should be 
fairly simple, maybe a small resistor could be added to prevent a large 
surge of current when it's first charged.  It wouldn't really replace a 
backup battery, but would probably enable you to unplug the CZ for at least 
a while without worrying about it.