More PT confusion

[lord preset]

I am barreling along with my high voltage Triwatt variant using the PT/OT from an old KMD GV100 amp. The GV100 was a near clone of a Musicman 65/100 circuit and voltage doubling is used to get 700v plates/350v screens.

I thought I had a plan for the power supply but re-examining the PT has raised some questions. At least to me.

The PT secondaries are laid out as follows:

Brown1
Black
Brown2
Purple
Grey
Red
Orange
Green

And the unloaded voltages:

Brown1-Black: 34.2
Brown2-Black: 34.2
Brown1-Brown2 68.4
Purple-Grey: 6.8
Red-Orange: 182.3
Red-Green: 274.4
Green-Black: 53v
Green-Orange: 8.5v

And relative to ground:

Brown1: 52v
Black : 37v
Brown2: 23v
Purple: 55v
Grey: 58v
Red: 56V

So from all this it seems that -
1. Red-Green is the HV tap
2. Purple-grey is for heaters
3. There are no center taps for the HV or heater windings.

As for the things that are less than clear to me:

1. Are the heater taps being ~50v+ above ground a normal thing? I never thought to measure this in previous builds. Does this prevent me from using an artificial center tap?

2. For the bias supply, I thought I would be using Brown-Black @ 34v. But not having a center tap for ground reference affect things? Would this design (attached) work?

Thanks!

[Tillydog]

An electronic DVM will give nonsense readings on floating voltages such as you would have with unconnected windings, or on any winding to ground with the transformer out of circuit. (If you got these voltages with a moving coil meter, then the transformer probably has problems.)

Figure out which wires are connected to each winding by checking for continuity first, then check voltage beteen each combination of wires on the same winding - it should become much clearer.

[lord preset]

An electronic DVM will give nonsense readings on floating voltages such as you would have with unconnected windings, or on any winding to ground with the transformer out of circuit. (If you got these voltages with a moving coil meter, then the transformer probably has problems.)

Figure out which wires are connected to each winding by checking for continuity first, then check voltage between each combination of wires on the same winding - it should become much clearer.

That is so blindingly obvious. And I so didn't think to do that.


Thanks

[Tillydog]