I have come across pitch drift on these machines before, it was caused by tarnished pins on the inter-board connectors (the flat connectors that link all of the circuit board inside). You could try pulling each one off, putting some Deoxit on them and re-seating them (making extra sure that you put them back on with the pins aligned correctly). If they are really black you can clean the exposed pins gently with a soft white pencil eraser and then wiping with alcohol before applying the Deoxit. The connectors on the SSK board on the bottom of the unit on the left are especially prone to this.
As for power, I would get a tech or someone that knows about electronics to check first, the general export model had multi-tap power transformers with taps for 100V, 110V and 130V, The Japanese model was only single tap at 110V and the US/Canadan a single at 120V. It would be worth checking inside to see if you got lucky and it is a general export unit and they can move the wire or replace a link to the 110 V tap which should be fine in the US. If there are muti-taps the voltages will be stamped on top of the transformer, or written on the circuit board. Take a digital photo of the transformer and power supply board and post it here and we can take a look.
The usual caveat applies, do not touch any mains section of your synth unless you are qualified and know what you are doing, and remove the mains plug from the wall before opening the top.
Synthesizer service tech since 1982.
Synth parts and service, Sydney Australia.