There are a few possibilities between a bad CRT, fly back transformer or a bad power supply.
One has to be careful as one can get seriously hurt poking inside. Between the high voltages still present even when turned off and disconnected from the wall as well as glass fragments firing off if you crack the CRT.
Someone with analog TV repair experience might be able to help you.
Do keep in mind the computer industry has moved quite far since this system was discontinued. You’ll have a hard time finding Apps and even the OS versions it supported have long since faded into the distance of time.