1993 ford festiva radio - always needs code input after turning car off!?

I've checked the power input to the radio with the ignition & accessories turned to the off position and there is still + potential to one terminal both sides of the plug going to the radio. I imagine thaty the is the + potential for standby mode to maintain the code as active. Whenever the car is turned off the radio returns to the input code mode. I bridged directly to this + standby terminal and the radio remains on all the time. Other than this, the system works fine when I put the code in, but it is really annoying having to put the code in every time I get into the car, or if I have it bridged, having to remember to to the radio off when I ghet out of the car!

Any help or suggestions to to fix this would be greatly appreciated