I started tinkering with a Timex Sinclair 1500 I was given awhile ago. When I first tried starting it, I got a K prompt in the lower left of the screen. I turned it off and did not return to it for a few weeks. Now, I do not see a K prompt when I try turning it on and even restarting it. Sometimes there are wide black vertical bars on the screen or small black squares in patterns. Has this machine died? I am using an old black and white portable analog TV with a dial for precisely tuning channels like 2 and 3.