Peter,

> I agree the two high voltage wires on the trigger transformer
> should be reversed

Ah-ha, now we're cookin'

It's a curious case of self-deception. If you compare my layout with
the author's

http://home.clear.net.nz/pages/joecolquitt/flash_proto.jpg

vs Figure 6 at

http://www.rory.co.nz/projects/lighting/beat_strobe.html

they look superficially the same, which is why I made the fatal
mistake of not verifying where those tracks were going. HOWEVER,
his voltage rail tracks are the opposite polarity wrt the transformer
compared with my layout. So, I've re-orientated the transformer
(at this stage by simply putting it on the underside of the PCB) so
that the common is to the tube trigger, not the 0V rail where it was

Activating the opto now produces a nice fat flash

> Also usually you will find a red mark on the positive connection of
> the flash bulb

Can't see any external markings, but the terminals are different, so
I'll check up on tube construction. The tube does flash now, which
is the main thing

Disappointing in one way to make a silly mistake like that but if
it wasn't for (occassional) dimwits like me we wouldn't get to pull
circuits apart ;-))

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