Question on reusing a Philco Transformer

[pompeiisneaks]

I've pulled a transformer from an old Philco radio, I've got the schematic, attaching the transformer pic here with some circled areas.  In this transformer, the B+ tap has a center tap, that is then tied into a resistor before ground, instead of straight to ground.  Do I need to do something like this in a tweedle dee?  Is this 'elevating' the ground a bit?  Meaning a voltage drop happens and it's technically not 0v at that 'ground point'?  This is an area I've never quite understood fully.  If not, why is it there, and do I need it?

~Phil

[sluckey]

That's an old way of developing a negative voltage. Show us the rest of the schematic so we can see what it's used for.

[pompeiisneaks]

If it isn't too big, here we go.

~Phil

[sluckey]

Yeah, it's used to supply the negative bias voltage to the fixed bias push/pull 6V6 output tubes. Very common in the late '40s and early '50s. Much better ways to get negative voltages since affordable silicon diodes were invented. You will just connect the PT CT to chassis ground as shown in your TweeDee schematic.

[pompeiisneaks]

Yeah I started reviewing it after you said that and I did see how that made sense, it goes directly into those 330k resistors off the 6V6's.  sounds good, I'll just tie that to ground as usual.

~Phil

[PRR]

Another way to see it:

This IS the cathode resistor for the 6V6es. Except it also carries the current for the whole tuner (and three small audio stages). So it will be a little smaller (150 instead of ~~250) and a little more stable against change-of-current as the power output is increased.

Do note that when worked without this minor (~~20V) drop, and the larger drop in the field coil, and especially with Si diodes, the raw B+ will be far higher than the radio final ever had. Of course this is how Fender turned 10W radio parts into the 20W 2x6V6 amps: tearing out all the drops designed in for radio parts. I dunno what you will get, though usually not much over 450V because of the limits of electrolytic caps.