When is it necessary to create a center tap using resistors?

[hesamadman]

Was curious when do I need to create a center tap on my PT 6.3v tap using 100ohm resistors. I thought it was when the PT itself did not have a center tap but on some schematics I am looking at, it shows both.

[sluckey]

I thought it was when the PT itself did not have a center tap

That's right. Talking about a center tap on the heater winding.

on some schematics I am looking at, it shows both.

Show us one of those schematics please.

[hesamadman]

I thought it was when the PT itself did not have a center tap

That's right. Talking about a center tap on the heater winding.

on some schematics I am looking at, it shows both.

Show us one of those schematics please.

Actually I apologize. I was mistaken. Since on the topic. Should the center tap of the 6.3v terminate at the PT CT ground lug as well?

[kagliostro]

Show us one of those schematics please.

Here you can see someone

http://el34world.com/Forum/index.php?topic=14449.msg136955#msg136955

But those aren't normal conditions, there you have a bridge rectifier that act as a "separator" and resistors are used as to recreate a virtual ground for the DC part of the circuit

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Sometime I've hear that in some cases (not good PT construction) some guy disconnect the CT and recreate it via resistors or Humdinger

I think that a Humdinger may be better than a grounded CT in the case of a not perfectly balanced PT, because you can perfectly balance the windings turning moving the wiper to the correct position

Franco