I do not understand why/if this mod works, and certainly whatever it may do in a cathode-bias amp it should do the same in any fixed bias amp. All it does is isolate the suppressor grid and have it float on whatever level it will get.
What level is expected : there is 2 mechanisms involved :
- surrounded by screen and plate one might think the suppressor will exchange electrons with it's surroundigs.
A/ It may emit an electron, by this it get more positive.
B/ it may be hit by an electron, capturing it, this will make the suppressor less positive
A and B will tend to balance , if the suppressor is very positive it will attract more electrons thus reducing it's positive charge. If the suppressor is negatively charged it might emit electrons thus increasing it's positive charge.
Still i cannot figure out if and how it actually does capture bounced electrones to prevent them from reaching the screen( the very reason the suppressor is added to a tetrode). Let's listen to what more experienced people has to say.