Alpine 7145l/7148L

[OXAUDIO]

Can anyone help with the following problem on an Alpine 7148L-the display is totally blank, and the tuning is in what I call 'free running' mode, i.e. it will scan the wavebands, but not stop, and none of the controls, other than the mechanical banswitch, have any effect. So far as I can tell the 4.5Mhz Oscillator is not working, and I'm beginning to suspect the microprocessor IC, in which case this 1984 or thereabouts stereo is scrap, but I have no schematic or service manual to help me check further. N.B. The +5v supply to the uP and other circuits is present, but there is no variable tuning voltage(unless I'm not checking in the right place!) I worked in the car audio repair trade for over 23 years, so am familiar with the principles of digitally tuned radios, but this one is a problem!!