18W Fluorescent in Series

1. circuit diagram electronic ballast for 18W tube l datasheet and ...
   
2. electronic ballast for fluorescent lighting* datasheet and application ...
   
3. 18w fluorescent driver schematic

Are you sure the starters are good?

Starters are difficult to measure, have you tried to start each of the separate bulbs with each starter one at a time to make sure you haven't just got a faulty starter.

Use of a single choke for both tubes does save some manufacturing cost. They are essentially connected in series, but each uses its own starter. The catch is that BOTH starters and BOTH tubes must be identical AND operational (and with not too much aging difference) for this scheme to work at all, so it's not universally used. S.M.

This is a method that is commonly used in commercial signs.

I guess the equation is something like one 36W ballast costs less than two 18W ballasts, and takes less time and material to wire up.

I have used this method myself from time to time. It can be a bit finickety to get going at first but seems reliable enough.

On a 230V supply, it is necessary to use 110 volt starters, and if our OP has changed out the starters without knowing this, that would account for the non-functioning of the light.

Since the stater we have in stock are all 220/240V I've changed it using two chokes.

Yes this method is cost effective and simple to wire up.

Thank you for your reply now I knew it next time it would be easy for me to repair this kind of circuit.