Yamaha PSS-270 question (dead or fixable)

[inactive]

Got a Yamaha PSS-270 a while back, knew it worked fine when I got it at least but now when I try to power it on, sometimes it doesn't do anything at all, but other times it will make a pop sound and i can hear a very faint high pitched hissing with LFO coming out of the speakers. Is it common for this keyboard to just...stop working? How might I go about fixing it? I opened the system up and nothing looks physically wrong.