Programming interface schematics for Kenwood :
Programming software for Kenwood TS-680S (TS 680 S TS680S) :
PDF User Manual for Kenwood TS-680S (TS 680 S TS680S) :
PDF Service Manual/schematics for Kenwood TS-680S (TS 680 S TS680S) :
Here comes some mods for the TS-680 which I found on a Japanese site.
The row of diodes are placed in the middle of the main PCB board.
Just cut off one end of the diode and lift it a bit up.