There is a capacitor on the mainboard in the ksu and there COULD be two smaller capacitors in the software cartridge. I am stretching my memory, but I think at DR1 the mainboard capacitor held configuration (with no caps in the cartridge) and by DR5 it was in the software cartridge that held the programming on its own caps).
If you have a quality soldering iron and some pcb experience, the change out is easy. The capacitors are 5.5 volt and either 1 Farad or 1.5 Farad. Most (but not all) were green on the mainboard and a bit bigger in diameter than a quarter and black in the cartridge, about the diameter of a dime.
I did a quick-and-dirty on a 616 DR5 by opening the cartridge, cutting the leads to the capacitors, soldering on some cross-connect wire and putting a dollop of glue gun glue in the top of the cartridge (there is a lot of room at the top that is empty). Glued the new caps in place and then soldered up to the cross connect wire. Worked just fine.
To find the capacitors, if you plan to use the quick-and-dirty, just look up the equivalent ratings as any capacitor will work (as long as the ratings are the same).
If you want the clean install, look at the suppliers of refurbishing supplies and you can find the exact capacitors pinned to fit the pcb.
Remember you are dealing with aging circuit boards with delicate traces so you need a light physical touch and careful temperature control when soldering.
Of course, be sure the unit is powered down and even then avoid shorting the capacitors when handling them (new and old) and observe anti-static precautions.