Calculating output transformer primary impedance from turns info

[composition]

Is anyone very handy with the theory and calculations behind transformer windings, specifically an output transformer for an amp? *I'd love to know the primary side reflected impedance (or impedance ratio) for the following transformer if anyone is knowledgeable enough to know how to calculate it from the winding information on the second picture. *I wouldn't really know where to start!





Winding 1 - 2 layers (37 + 37 winds), wire diameter 1mm.
Winding 2 - 2 layers (94 + 110 winds), wire diameter 0.3mm.
Winding 3 - 7 layers (each 118 winds), wire diameter 0.3mm.
Winding 4 - 1 layer (43 winds), wire diameter 0.9mm.
Winding 5 - 7 layers (each 118 winds), wire diameter 0.3mm.
Winding 6 - 2 layers (110 + 94 winds), wire diameter 0.3mm.
Winding 7 - 2 layers (37 + 37 winds), wire diameter 1mm.

Thanks!
Jonathan

[Dave H]

It looks like primary orange to blue is 2060 turns. Secondary black to yellow is 117 turns. A turns ratio of 17.6 = an impedance ratio of 17.6^2 = 310. A 16ohm speaker connected to black and yellow would reflect 4960ohms (plate-plate) to the orange-blue.

Dave H.

[tubeswell]

Pr:Sec turns ratio = Pr:Sec VAC ratio. You can work out everything else from there

[Chuck H]

And that isn't to mention that there are a whole bevy of peripheral criteria for performance. Most of which I can't explain, but have been explained and considered here before. The turns ratio and reflected impedance is only part of a transformers duties. A transformer also has core and copper losses that figure into it's capacity and inductance that equates to frequency accuracy. It would probably be better to know more specifics about the transformer and the goal of the project.

[J M Fahey]

Hi composition.
Fine, but you provide us with half the picture.
We can *guess* but may err because of that.
Please provide
a) core dimensions. At least the bobbin core dimensions , we can use that to estimate what EI sheet size was used, but even better, bobbin core ("hole") dimensions plus EI width and height.
I guess you patiently unwound one such transformer and have all parts separated on a table by now.
Are you rewinding a burnt transformer?
In that case, what amp did it come from?
Or are you cloning an old one and got this data somewhere?
You provided us withn wire diameter.
Fine, copper is copper and didn't change at all along the years.
Buy transformer steel has changed a lot, and generally for the worse.
Not that knowledge is lost, but manufacturers in the 50's could spend a lot of money and still sell; today it's cut throat competition, so maybe even if you clone one with the exact same turns, the sound may differ.
Doesn't apply if you are rewinding on an original core, of course.
Good luck.