Quoted from Insane:
I put a new Sr20 in I don't remember if I checked it first. I will. Should I have any reading from Sr20-1 to ground, because I do' also since I don't have the correct reading from pin 8 - 1 like you said something in the circuit is giving it an easier path without going through the resistor. What components are there and I can start checking them. With the transistor being cracked in half when I started, I'm sure this whole circuit area could have other bad components.
Reading from SR20-1 to ground is measuring Vcc to ground. That's basically a useless measurement for what we are trying to accomplish. You would be measuring EVERY component on the entire MPU board attached to 5VDC and ground.
We know where the signal is fine - up to the U49 buffer. Then we have eliminated it's path downstream by removing U45. There's just a few components in this local area: the pullup resistor on SR20, the cap 71 to ground, and the output of U49 (we know it's input is good, I am trying to help you figure out why its output signal is not)
Since we have a bad measurement to Vcc on your pullup resistor, someone is conflicting with the pullup. It's not U45, as that is out of circuit. You had a pin not in the socket on the pullup, now if SR20 is installed correctly, and was measured fine before installing then you can eliminate that. Cap 71 to ground doesn't figure into the equation since it is connected to ground and you are measuring from the circuit to Vcc (unless it was somehow magically shorted to Vcc) so forget about that one for now. All that would be left would be U49 (failed output, shorted internally)
That's what I am interpreting from the previous posts.