tracing out schematics

[Tony Duell]

> >  Now what happens if you add the choppers?
> 
> try the whole PSU with the bulb in place, or isolate everything
> downstream of the choppers and just try those hooked to the DC output of
> the bridge? (i.e. by removing the main switching transformer and the
> small transformer that drives the gates of the choppers I should be able
> to isolate everything else)

I was going to suggest running the entire PSU, but in this case, can you 
find the drive from the chopper control chip to that driver transformer? 
If so, disconnect it and see what happens. If the bulb stays bright then, 
I think you have a short somewhere on the primary side. If not, then 
either there's a short on the output side (but the protection circuit 
should cope with that!), or the copper control circuit is doing crazy things.

-tony