Why is my flash not reloading power and thus, not firing?

Hello All,

I have a problem with my Canon 430EX II Speedlite. It doesn't want to fire anymore. But , to my frustration and juste to give me some hope, it fires occasionally (usually one time only just after powering it up but not always). It looks like it doesn't charge the capacitors anymore... or something like that.

What do you think could be the cause ? I would like to be able to repair it. The tube isn't broken because it still fires. I don't understand.

Thanks,

Martin.