Some one correct me if I'm wrong, but the schematic is not a visually correct map. It's just a map of what connects what, like wiring schematics for cars.
V1A and V1B are the same tube, right? If you look at the schematic (not the function descriptions at the bottom), V1A connects to the input directly. Open the unit up, and follow the wire from the input jack to the tube socket, and that should be V1.
Don't give up, someone will read your other post & give you the info you need.
In my .50 Caliber, V1 is the first on the right if you are looking at the amp right side up from the back. The preamp section in mine should be very similar to yours.
Give it a good cleaning with an electronics spray while you've got it open.