Is there a tape in the VCR by chance?.
Usually what happens on these combo units is the VCR develops a mechanical problem which inhibits the whole thing from working or overloads the power supply causing it to shutdown.
The ones with the VCR underneath are difficult to work on as the cables to the VCR are so short you have to disconnect it in order to get it out where you can see what is going on, then work on a solution, put it all back together, test it, rinse - lather - repeat. Takes forever sometimes. Find a good VCR tech and talk to him nice and maybe they will help you.