I have a question about the use of the TT double relais switcher kit. The provided schematic shows that for its power supply it's supposed to use the 6,3V also used for heating. After reading some about this topic in Blencowe's book, I started wondering under which conditions the heating votage can be used to power the switching.

In the case of heater elevation, Blencowe seems to say it's absolutely impossible to use. Or is this incorrect?

What about using heater winding with a center tap and more specifically an artificial center tap? From what I understand, the danger might be in shorting out the rectifier part.

Thanks a lot

https://www.tube-town.net/ttstore/Kits/Needful-Things/Kit-Double-Relais-Switcher-6-V::5910.html