message to program channel scan Television Model #626.54465090?

We have an LXI big screen TV that was purchased back in 1991. We no longer have the remote and need to change the input. I tried using our Comcast remote and using the buttons on the TV itself with no luck. It was working fine until a power outage early this morning. I unplugged everything and plugged it all back in. I called Comcast and they walked me through a few steps but still no luck. I would rather not pay a service tech to come out if I can do it myself. How can I access the input? Any ideas?