Impossible to say what’s wrong, but bad electrolytic capacitors are a common problem, are cheap to replace, and not hard with basic soldering skills. First search the web for a disassembly guide or video, and if you can’t find one, just remove screws from the back until it comes off. (Make a note of where they come from if there are several sizes). Bad caps are often easily spotted if they have domed tops or showing signs of leakage, but they may still be bad if they look good. Take a look at https://wiki.restarters.net/Basic_electronic_components#Fault-finding_and_Repair_3 for more details.