I have a question.
I'm not really god at the tecnical stuff, but i wonder how much current is running through the trimpot? I have a mini Piher pot that is rated for 100V. Will that do?
Anyone?
Oh Gawd, another forum to watch....
The 1K trimpot is in series with a 220k resistor (and a 470R resistor) from a nominally 200V supply, so the current (I = V/R) is roughly 200 /221,000 i.e. <1 ma.
Most of the 200V will be dropped by the 220k fixed resistor, so your 100V pot will be fine

Someone above asked about output impedances... for the original circuit ~25k is reckoned to be optimal (by DougH, the designer), but the schematic was drawn when he was using a lower impedance, hence the confusion over the connection numbering. For the sub-mini version, it's anybody's guess. Particularly as the information on the 7327 is scant.
Incidentally, if you're in the UK, then the RS components 3.5W output transformer works well (better than the 125A IMHO) and is <£10. You need a slightly larger box to fit it on, though.
It's a cute project

(That's my hand in reply#168)