Simplistic Mosfet HV Shunt Regs

[merlin el mago]

To adjust Vout I'm using 1K trimmer

[nemo1968]

Hi
Which is the minimal allowed Vin for this shunt to work properly.I need the voltage from 100 - 150.I don't have higher voltage transformers but only 110 - 130V on secondary and want to try the shunt.I use lot of subminiature valves with limited max. voltage possibility and this way the tubes would be protected to not get 250V in case of shunt failure with 250v input voltage (if I understood well what happening with the regulator failure).

Is that possible with filtered 150 - 170V on the shunt input?

Thanks to Salas and everybody around the shunt.

[Salas]

There is no downwards limit.

[nemo1968]

Thanks Salas. I was afraid of oscillations and eventual failure in that case.

[Salas]

You can make R3 33K so to keep around 5mA through the Leds when under 200VDC input too.

[nemo1968]

Yes, I was just in doubt which value to put there because of over 300 and under 300V R3 mods.

Thank you, again Salas.

[merlin el mago]

How to test CCS because LEDs don't lit & I have checked IRF9610 with a DVM & it's not crossed, also I checked proper oritentation LEDs also lit with 9V battery

[Salas]

Just check connections against schematic, exchange Mosfet, the usual troubleshooting.

[merlin el mago]

Fixed, was IRF9610

[pedefede]

Originally Posted by Salas

Bypass C2 with Teflon if you can. Then we roll big way.

Since C1 also is important:
- can you bypass it as well
- i suppose so - but should the bypass cap be over just C1, or over both C1 and the 47ohm resistor?
- should the bypass be closest to the LEDS, or the mosfet?