My old man still has his first computer, a ZX-81. Tried to get it working a few years ago, but couldn't get it to display on the TV. Wasn't sure if it was even

My old man still has his first computer, a ZX-81. Tried to get it working a few years ago, but couldn't get it to display on the TV. Wasn't sure if it was even powered on because the thing has no lights on it, it was prior to LEDs being commonplace. I didn't have an oscilloscope or the skills to debug it. Having just finished off 4th year embedded systems I'm probably a bit more qualified to debug it now than I was in high school.