Depending on which version of Pro Jr you have you will need to wire the connections from the main pcb to the tube pcb differently. See the pics for your version of the amp.Wiring connections from main PCB to tube pcb are in yellow on the diagram. The diagram is oriented looking from the tube socket side of the chassis.

There are two different ways of wiring for the Fromel tube board: for the newest Pro Jr IV with a black PCB and every other version of Pro Jr. Only use the wiring diagram pic that is for the amp you have.

All of this info is also printed on the PCB