The reason it did not power on was that a small tab of copper or copper plated steel that actuated the power switch had been knocked off the switch.
in order to get the top of this unit off remove the screws circled in red, to get the bottom plate off remove the red and the green circled screws.
The schematic is inside the stereo under the top cover. If yours is missing here is a very high resolution scan. Dial string instructions included.
Or you can download a pdf that contains it, and better printable copies.
When it asks you to login or create an account click "no Thanks, Continue to View"
Then Click Download in the upper right corner.