its possible for heads to fail, but it wouldn't be at the top of my list. Its two coils of wire in a metal box. Having both go open seems odd to me. Should be able to confirm it with an ohm meter. If they aren't open, chances are very high that they are capable of outputting something.
+1 on touching the wires on the head though. If it hums, the audio circuitry is working. If nothing, my bet is on the tape head amp circuitry is not working for some reason. Not looking at a service manual but if there is a switch between the tape head and the head amp input, I'd focus on that. Switches IME are more troublesome than most electronic components.