This is an 8080DB right? If so, the dial lights should be on whenever the power is on.
Are all the lights out or just the dial lights? Are the power meter lights on? If any light other then the FM stereo light is on, the power supply is OK and you have a circuit problem. If ALL the lights are out (except the FM Stereo light), you have a power supply problem.
The lighting system is AC voltage. Set your voltmeter to AC voltage and check the voltage between each of the terminals of fuse 03 and chassis ground. If you have voltage on one side but not the other, the fuse is bad. If you have voltage on both sides, your problem is down stream.
The x0x0 series is famous for bad solder joints on the fuse lamp holders. Bad solder joints will give you the symptom of the lights going on or off when tapping them. Put your AC voltmeter across the lamp holder and see if the voltage fluctuates when you tap it.
- Pete