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Hi Folks,I’m trying to track down the manufacturer and the specs for a pair of mystery output transformers (one of the pair is shown above). I would appreciate any help you could provide. I was told that they are for building a parallel single-ended 211 amplifier. They are huge, as you can tell from the dimensions, almost 20 lbs. of iron and copper.
Dimensions:
--Height: 133 mm
--Width: 111 mm
--Length: (end bell to end bell): 150 mm
--Weight: approx 9.1 kg.The transformers have a serial number of FM 6697 and appear to have been manufactured (or custom wound) in 1993. The laminations also have the characters D.T2 stamped on them. Maybe that’s a clue.
Maybe you have a pair of these. If so, I'd like to learn whatever I can about them (primary impedance, how to configure the output leads for 4 and 8 ohm speakers, etc.).
Follow Ups:
For PSE 211's they are probably 5K. I see they may follow the standard color code - red to B+, blue to the plate (that's the primary); black is output common, usually brown is 4 ohms, orange is 8 ohms, and yellow is 16 ohms.
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.
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.
If you want the primary Z, it is fairly easy. Grab the plate lead and B+ lead and plug them into the 120V wall. Measure voltage on the 16R secondary. Divide wall voltage by secondary voltage, square the result and multiply by 16 to get the primary Z seen with a 16R load hung on the secondary.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Thank you for suggesting a measurement method. I'd like to do what you suggest, but am not sure how the output leads are configured, that is, which lead is the common, which is 8 ohms, 16 ohms, etc. My reply to Paul Joppa provides more details on this part of the problem.
I love a good mystery. I have spent many hours figuring out what use various unmarked transformers were intended for.Those thin primary wires don't look like they have the insulation properties required for the 1KV or so you would have in a 211 SE amp.
Can you tell us where they came from?I once bought 3 large unused transformers on ebay that the seller indicated were unmarked and that he knew nothing of electronics. When I opened the box, the mystery lasted but a few moments. There was a small tag on each that said GTA***. The *** was the model number (I can't recall it at the moment) of the Golden Tube Audio SE amp that used 3 5881s in parallel. The same seller had sold one earlier. The guy that bought tried to buy one of mine, I tried to buy his....we never worked it out. I contacted the seller in the hopes he had other stuff from GTA, but he couldn't even remember where he got them from.
You make a very interesting point about the primary wires. They really do look too delicate to handle 1 Kv or so. The unfortunate reality is that the original purchaser is dead. So I rather doubt that I will ever learn the true provenance of these very substantial pieces of iron.
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