Help with this YAMAHA QX21

I recently inherited this sequencer from other synthesizers and devices of the time, including a dx7, everything has worked wonderfully for me except for this instrument, I connected it and turned it on, it seems to be frozen, it generates a somewhat annoying noise like a converter and the lights stay on and does not show anything other than that message, I have already tried pressing the buttons or searching for errors but there are none with those acronyms, I need help to know what it could be in this case and what the procedures would be to be able to restore it and use it again