Have you checked any of the internal tube voltages?
For instance, the filament and plate voltages. The owner's manual schematic is short on listing circuit voltage values, but you should at least see 6VAC for both tube's filaments. And, of course, they should be lighting up.
Can't tell what the plate voltage(s) should be but you might check what value AC is being supplied to the rectifier "X1", and then see if there's any DC value on the other side of X1 (I"d expect something like 150 to 250VDC).
Be careful. There are lethal voltages present.