Audio Systems: 1990 Ford Ranger Radio, ford ranger pickup, hands free phones

Question
1990 Ford Ranger Pickup Truck

I had an after market radio/cd player in the above vehicle.  It went bad so I put the factory radio w/cassette back in it.  The factory plug-ins were still in the vehicle.  The cassette player works however the radio does not.  I just get static and none of the controls work, such as the tuner, scan, or seek.  Nothing appears in the little window display.  I would appreciate it if you could help.  Thans in advance.  Ron.  

Answer
When you say "the cassette works" do you mean it plays and you can hear sound on the speakers or that it loads and unloads?
I would first check the power leads at the head unit connector to see if I had all the right 12v connections which basicly are, 12v perm, this powers the unit, 12v ACC, this switches the unit on with the ignition but does little else and 12v OUT to amps, electric arials, etc and is live only when the radio is turned on. there is of course earth, sometimes lights which dim the display at night and sometimes a phone mute lead for hands free phones.
check it out and let me know.
Peter