Hi Roger,
If you look at the bulb (don't touch the glass) it will be obvious if it has blown.
If you have a scope you can get some interesting waveforms from the wiring to the bulb and also using a inductive amps clamp.
Beware though initial volts to strike the arc are approx 18 to 27Kv then upto 130v AC pulsed at 400Hz to maintain the arc.
If you suspect a faulty ballast module you can substitute the one from the other side to confirm.

Hope this helps, I have lots of Bosch info on these if you need it.


Mark