Vintage Synth Repair

Dear list,
i bought recently a siel expander, dk-600 tabletop module version.
after messing with sysex informations found over the net i was able to program
it from my windows computer(despite what someone says, handshaking is not
a must, so programming it without the keyboard version is possible.)
So far i was happy.

Of course the day i opened the machine up i found the dreaded battery leakage
problem. I decided to try cleansing it and apparently succeded.
But soon it started behaving strangely, so i took it apart again and found
a capacitor leg broken! i don't have the facilities nor knowledge to solder
it on my own (i can hear you laughing) so i abandoned the quest.
Today, after a month of inactivity i pushed the on button and the poor synth
seems to be DEAD.

My humble questions are: can a single capacitor disconnected kill the machine?
i could run it without capacitor a month ago, the machine would freeze itself
after a minute or so.

Also i read about korg polysix not to touch the inside without antistatic
precautions not to burn cmos circuits. i dont know if it is the case, but
i didn't took any precaution. And anyway between dk600 life and death passage
i didnt touch it no more, so it must be something i did that killed it slowly
during the month of inactivity. It shows no sign of corrosion now, traces
are intact.

any advice anyone?
thanks, davide