Simplistic MosFET HV Shunt Regs

You said before that voltage goes up when you reduce current. When your output voltage is right measure Vbe and Vgs on all the semis.
Also try with an easier dummy load 10 to 15k.
See what happens when you up the current. Readings change?
My impression is that something is wrong on your setup and reg is working fine.
I built it many times and it' s difficult to go wrong.
 
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Great balls of fire:flame:

R2 disappeared & R5 burned, possibly D5 & D6 damaged:down:
 

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iko

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Joined 2008
Don't be so harsh Andrew; the moment you make PCBs available you will have to expect that people have some expectation of solder, plug, and play.

However, Andrew is right in that you need to be very careful with these high voltages. Someone should post a little guide of how to first test these regulators once soldering is finished. Dummy resistor, current calculations, etc. This may have very well been done, but I don't know it because I haven't been reading so carefully the thread lately.
 
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Changed all semis, diodes & burned resistors.

Max. current reached 319mA I read 0,319V across TP, Vout with this current 281V but can low the voltage to 240V the voltage is fixed 281V

If I reduce the Vout with R4 trimmer (used for adjust current) I can reach 240V but the current must reduced to 275mA I read 0,275V across TP