Credit goes to David Duffy he first spotted it I just mentioned it again
to make sure you read it.

Peter



----- Original Message ----
> From: Jinx <joecolquitt@clear.net.nz>
> To: Microcontroller discussion list - Public. <piclist@mit.edu>
> Sent: Friday, July 17, 2009 8:10:57 PM
> Subject: Re: [EE] High voltage opto-coupler
> 
> 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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