When you say it does nothing but lights, do you mean the 8-track part only, or the radio tuner too?
If none of the 'electronics' part works, the first thing to check would be fuses...its not uncommon for there to be 1 fuse for the lighting circuit and another one or 2 for the electronics.
Also don't operate these old stereos without speakers attached! Some of them will literally go up in smoke if there's no load on the amplifier output!
On some they will light with no cartridge inserted, the button for changing tracks will even work. With others you need a cartridge.
Its All For The Christmas Lights...
And A Good Summer Thunderstorm!