Part of my error was I was using only 1/2 the winding: the center tap to one side. Also my voltage ratio is actually 19 v / .5 or 38. 38 X 38 = 1444. 1444 X 8 = 11552 which is closer to the spec of 10,000. I'm thinking measurement error accounts for the discrepancy.
I put a 10 ohm load on the 8 ohm winding and wired a variable resister in series with the full center (not used) tapped side, I applied a 1KHz signal to the winding and variable resistor (in series). I adjusted the variable resistor until I had (almost) equal voltage across the winding, and then the variable resistor.. When measured, It was close to 12,200 ohms.
Again , I'm thinking measurement error.
Do you think the spec 10,000 ohm Plate to Plate is a "nominal value" ?
The reason for my experiments is: I have a junk box full of unmarked audio transformers and I would like to know their values. It's relativity easy to find the turns ratio, but measuring actual matching plate resistance is somewhat of a challenge. If it's nominal /marginal, maybe it's not that important.
It absolutely is a "nominal" value. I have made impedance measurements on a bunch of "identical" transformers, using a high end impedance analyzer, and it's quite typical to see variations in measured impedances of around 10%. There are many variables in the building of transformers, such as the tension provided by the winding machine, losses in the laminations, variations in the diameter of the wire used in the windings, etc.
Don't miss this reference given in the references provided by "The Electrician".
http://www.jensen-transformers.com/an/Audio Transformers Chapter.pdf
Pay particular attention to the section on "Realities of Practical Transformers" and the parasitic elements that are part of the transformer circuit model. While the transformer designer has supposedly done his best to minimize the effects of these parasitic elements, please realize that while your test setup is trying to measure the performance of the 'ideal transformer'
these parasitic components are a part of the test setup and do have an effect on your measurements. Of course, if you knew the actual values of these parasitic components, then it would be possible to account for their effect in your test calculations. Might there be some clever way to devise a ratiometric test that would cause parasitic cancellation? Just something to think about.
This is of the essence. I put it much stronger in the thread on two ports I linked to.
The existence of the various parasitics is just what causes the transformer to have an optimum pair of impedances between which it provides the best performance. If it weren't for those parasitics, a transformer (an ideal transformer, in other words) would provide the same performance between any impedances having the same ratio (the square of the turns ratio).
Rather than try to make a measurement that cancels the parasitics, just measure the image impedances. Those are the optimum impedances and are the impedances that the manufacturer (ideally) would specify (and design in) as the rated impedances of the transformer. The image impedances take into account the parasitics without any need to derive them separately.
To measure the image impedances, I explained in the linked thread:
"If you want to know the "rated" impedances of an audio transformer, find the image impedances. The best way to do so, is to use an LCR meter and measure the impedance at the frequency of interest with the other winding successively shorted and open and take the geometric mean of those values.
A method that can be done with minimal equipment is this:
Use an audio generator with a low output impedance; 50 ohms will be good. Connect a potientiometer whose maximum value is several times the expected open circuit impedance (Zoc) in series with the primary winding. Set the pot to zero ohms and set the generator to 1 volt or so. Connect a DVM on AV millivolt range to the secondary. Make note of the secondary voltage with the pot set to zero ohms. Now adjust the pot to higher resistance until the reading on the DVM decreases to 1/2 the value when the pot was set to zero. Disconnect the pot and read its value with an ohmmeter; that value is approximately equal to Zoc.
Disconnect the potentiometer and connect a low value resistor (perhaps .1 ohm for our output transformer; for an arbitrary transformer, use a value of no more than one tenth the expected value of Zsc) across the secondary. Connect a different potentiometer as before, but with a lower maximum value, perhaps several times the expected short circuit impedance (Zsc). Set the pot to zero ohms and set the generator to 1 volt, or so. Note the reading across the low value resistor connected to the secondary, in millivolts on the DVM; adjust the pot until the reading is reduced by 1/2. Disconnect the pot and measure its value with the ohmmeter. That value is approximately Zsc.
Calculate the value of SQRT(Zsc*Zoc), which is approximately the input image impedance, and which is a good approximation to the "rated impedance" of the primary winding.
The transformer windings can be reversed to find the image impedance of the other winding. It might be easier to also measure the voltage transfer ratio and use the square of that ratio to get the nominal impedance ratio. That impedance ratio can be applied to the primary image impedance to get an approximation to the image impedance of the secondary winding."
