MG Car Repair: Electrical problem, purple wire, fresh power

Question
I have a 1979 MGB that I am having a problem with the radio.  If I turn the ignition to the "on" postion, the radio works.  However, once I continue on, and start the engine, the radio stops working.  The radio doesn't work while the car is running.

Answer
Hi Ernie.  The radio is wired from the accessory connection on the starter/ignition switch.  It should cut out when you hit the starter, but come back on when you release the key with the engine running.  This part of the lock mechanism is a bit unreliable.  

Personally, I would rewire the power to the radio so that it will work all the time.  I would disconnect it and then take a fresh power supply from the purple wire attached to the back of the clock.