Yaesu FT-50R battery drain

Question

My Yaesu FT-50R will drain a battery in just a matter of a couple of hours. I think there must be a short because the heatsink gets hot (even when the unit is off). I purchased the unit new in either '98 or '99. I chenged the k**b out a few years back, and that has been the only other problem. I hope you can help.