OK--you can't show me any decent, self-consistent, or believable documentation on the layout and schematic.
Therefore, you must try troubleshooting it yourself, following what you can see of the circuit.
I suggest you connect your generator to what you believe to be "LI" = left input, and also to Ch1 of the CRO.
MCAmp.pdf (17.34 kB - downloaded 122 times.) , and start with power off.
Take your x1 probe (or x10) and start with where you think LI is on the PCB, then go to the emitter of the input transistor.
You should see almost the same thing when you probe those two points
on the PCB.
If you pass that test, then you can turn the input level down to a reasonable level for this amplifier, apply DC power, and probe from that point to further points down the two-transistor amplifier chain (CRO AC-coupled).
That would be a good start.
I contend, given the information given me, that you have accidentally connected the generator to an output of the amplifier.