[aprssig] Kenwood TR-7730 backup battery?

[Greg D]

Hi folks,

My packet station and iGate runs on an old but quite serviceable Kenwood 
TR-7730.  The rig has a connector in the back for a backup battery, but 
none is present, so any momentary glitch in power send it back to 
defaults.  I have not been able to find a battery, nor the pin-out and 
specs to fashion one of my own.

There appear to be 3 pins in a triangle formation.  Anybody know what 
the spec is?

Thanks,

Greg  KO6TH