Discussion about the Korg PolySix synthesizer

Hi folks!

My Polysix after battery leakage had the typical symtomps you might 
expect. 

After having cleaned & resoldered the guts everything's fine apart from 
the memory; 
I create a patch, I press WRITE, I choose the location. Seems OK. But 
just click another patch, then come back to the one I just saved - and 
it's not there. A new 3.6V battery has been installed, but it is not 
the matter of battery, beacause we are talking about doing this when 
the synth is still operatnig, being plugged, so it has all the power 
needed all the time.

I'm inclined to think the TC5514 S-RAM chip is the culprit, because all 
the chips keep voltage of 5V whereas this one has just 4V.

What do you think ? What replacement part for TC5514 should I look for?
I've heard about Intersil HM6514 and Nec uPD444c (D444C-6514) but are 
these really the only ones? I came across some chips with 'similar' 
characteristics and I really would like to avoid importing the above 
mentioned ICs.

I'm not a tech, but a tech's opinion would be greatly appreciated and 
helpful.

  cheers
  aero