[Dekatron]

That ohms check is about right, there is a 10 Ohm resistor across 1 and 2.

The next step would be to hook up a meter across the red and brown connections on the oscillator board and see if you have the correct signal there.

Then you'll have to check if you have any signal across the output transformer of the oscillator on pins 4 and 5.

If all is correct this far you'll have to try and trace the fault in the amplifier, it could be as simple as a lose wire to/from the amplifier, perhaps to the meter, or a wire that has been pegged beneath any of the standoffs so that it has become shorted to the common ground.