Yeah, normally a RAM or ROM fault. You can tell if ROM is running or not because the diagnostic cartridge should theoretically boot... Or you can use a oscilloscope and checked the ROM chip enables to see if they are switching power up or not...
If the ROM chip enables are pulsing several times at power up, then the machine is at least attempting to boot, which generally indicates the machine has a RAM fault... And of course the floppy LED will not blink unless the operating system is running which of course needs working ROM and RAM.