Well start with taking some photos of the power supply board, and if you have not been working with switch mode power supply smps
before be careful if you had it plugged into the net the filter capacitor can be charged with 200-400V so do not touch it or
use a dvm to check and see its discharged.
Then trace backwards on the 12V and try to locate the fault, most common fault is bad solder connections and capacitors
But start with a few good quality photos so all parts and text are easily readable.