Blocked drainage tube in fridge?water spilling over from channel?

Hi, I have an old electrolux TR70/55 fridge/freezer ,About 30 yrs old) the drainage from the fridge has stopped , i have pushed a flexible tube down the drainage hole but it stops after it has gone down about 4 foot ( about halfway down the freezer from the fridge, i cant see were the tube comes out although i would think it should go to the evaporation tray at the base of the freezer, have looked but cant see any tube coming into the tray. The fridge/freezer is built in and i didnt want to take it out to see what is blocking the tube or verify the route it takes, any suggestions would be appreciated.