Raise VR tube string's output voltage

[Hearinspace]

If making a pentode screen voltage supply using cold cathode VR tubes, can the voltage at the screen connection be raised above the VR tube's voltage by using a series resistor?
I'm thinking that using a potentiometer would give some fine tuning capability but don't have enough experience with cold cathode VR tubes to know if the added resistance can create problems. I have 100V rated tubes but want to add 50-60VDC.
If OK, would it be best to put it at the top of the string (Vout to screen) or at the bottom ( connection to the pentode's cathode)?

Thanks !

 

[audiowize]

This really depends a lot on the currents involved. I've tried this before, and I've only had success when the current demands of the screen were tiny and I could run lots of current though the shunt reg tubes.

A simple series regulator will free you up to have whatever DC voltage you want!

 

[Eli Duttman]

Why fuss with a "shaky" method? Use 1 or more Zener diodes under the gas discharge tube(s) and get the g2 voltage exactly where you want it to be. Bypass the entire VR stack with a 0.68 μF. film cap of good quality and appropriate WVDC.

 

[DF96]

Using a resistor to boost the voltage also means boosting the g2 supply impedance, which defeats the point in using a regulator. As the resistor is in series with the regulator it does not matter whether it is 'above' it or 'below' it in the chain.

 

[Hearinspace]

Well, there we have it, a bad idea all 'round. In the can it goes.
Thanks