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In Reply to: Re: Can you identify this mystery transformer? posted by Paul Joppa on December 2, 2006 at 18:58:07:
Thank you for taking a stab at this. Yes. I'm guessing that the primary impedance is 5K, as you say, but would like to take Sector-7G's advice (in a different reply) and attempt a measurement as well.The view from the bottom (which wasn't in the original post) suggests that the connections may not be as simple as you suggest. I'm almost certain that the two thin wires on the left (red and black) are the primaries. Both are stranded (unlike the three wires at the right). A resistance measurement gives 154.2 ohms, implying that they represent the two ends of a single wire. Also the resistance between either of the two wires on the left and any of the three wires on the right is infinite, suggesting that the wires on the right are the secondaries. If left is primary and right secondary, it seems that the primaries (black and red) don't use the standard color code after all, unfortunately.
Now, on to the three wires on the right. What I believe to be the secondaries are yellow, orange (which looks red in the picture), and blue. The yellow wire has one solid conductor, the orange has three, and the blue has four. So, the secondaries have no black wire at all. As a result, I don't know which wire is the output common. Is the one with four conductors (blue) the common? That might mean that the orange is 8 ohms and the yellow 16 ohms, as per the standard. Or is it 4 and 8?
So, I remain confused about how the secondaries are configured, that is, which wire is common, which represents 8 ohms, etc. Maybe knowing more about how the secondaries are constructed (single wire, three wires twisted together, and four wires twisted together) will give you more food for thought.
Follow Ups:
Too bad - it seemed like such a good guess!I assumed the fat wires had thicker insulation, for the high voltages that 211s run at. Since they were the standard colors for a vacuum tube SE primary, it seemed a good guess - but totally wrong. I still can't imagine why anyone would violate the code when it's so easy, and so helpful to the user.
Hard to say what the meaning of multiple wires is, without knowing the winding geometry. If the 3- and 4-wire bundles are insulated magnet wire, that might mean multiple interleaved windings, brought straight out rather than terminated to leads on the inside. Even so, that doesn't tell you much. Even if we knew the thickness of the wires (are they different?) it's too uncertain what is going on.
So ... you can't deduce the secondary impedance from the color code. Therefor when you measure the ratio, you still won't know the primary impedance. Assuming the secondaries are in the right ratio to each other, you might reasonably guess they are 4 and 8, or 8 and 16 ohms. Assuming there is not a tertiary feedback winding!. But which one? Is it (for example) a 5K or 10K primary?
To really answer the question without finding the winder, you can measure things like the inductance, the maximum DC current, the leakage inductance, and the effective primary capacitance. Then at least you can assess its utility for various impedances, whether or not those impedances were intended by the designer. But now this is starting to turn into a research project ... :^)
Exactly. This can easily become a big research project. It would be so much easier if folks would follow established color-coding conventions, as you rightly point out.Yes, all the individual wires in the secondaries are the same gauge--even though some are twisted together into larger composites. My guess, too, is that the wires are interleaved in some configuration or other.
Learning the name of the manufacturer would perhaps be the best outcome, but that may not be possible so long after the original manufacturing date.
Hi,
What ever happened with those unidentified transformers?
I ask because, in addition to curiousity, I am about to wind my first pair of output xfomers and I will be buying E-cores, bobbins, endbells, etc. If those are just collecting dust perhaps I could buy them from you to re-wind them.
I also have 3000+ square feet of vintage audio gear, tubes, parts, documentation. etc., etc,,,,,,,,,,,, If you need something and would like to do some trading.Please let me know.
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