Questions about a Vintage Stancor Transformer

Discussion in 'General Electronics Chat' started by MicroMike, Feb 20, 2013.

  1. MicroMike

    Thread Starter New Member

    Sep 30, 2012
    12
    2
    Greetings all.

    I've recently come across a Stancor transformer that seems quite old. Old enough that it has braided cloth insulators on the wires. It seems to have acquired a coat of black enamel at some point in its history so I have none of the usual labeling to work from. It has the brand name and a pair of numbers stamped into the casing but neither number has gotten me anywhere in terms of searching for specs so I assume they're a serial number and a date code or the like.

    I'm looking to test the output voltages but I've little experience with iron core transformers as I've mostly dealt with switching supplies in the past but from what I understand the smaller wires with higher resistance measurements are typically the primaries. The bit I don't understand here is there's an odd number of wires, 11 to be exact, all of them in colored pairs save one. There's a pair of orange wires that read around 180Ω (Highest reading on any pair) but next to them is the odd man out, an orange and yellow striped one that reads around 90Ω when paired with either of the orange wires. I assume this is for the purpose of having both 115v and 230v inputs. The questions are, which is which? and can I do any damage hooking the wrong pair to 115vac line power?

    Thanks in advance for any help.


    -Mike Bilan
     
  2. SPQR

    Member

    Nov 4, 2011
    379
    48
    HERE's a link that might give you a start.

    And THIS one looks very nice.
     
    Last edited: Feb 20, 2013
  3. nsaspook

    AAC Fanatic!

    Aug 27, 2009
    2,907
    2,163
    What are the codes? If it starts with 138 then that's the STANCOR EIA code

    http://www.preservationsound.com/wp-content/uploads/2011/10/Stancor_1937_Transformer_Specs.pdf

    Don't use full line power to probe the transformer, use a variac (with current meter) or a low power bell transformer (power limited) until you have good idea of the layout. If is a fairly large power transformer the primary resistance should be pretty low (only a few ohms), high resistance windings are usually HV (several hundred AC volts) outputs, very low resistance winding are usually for filament power.
     
  4. MicroMike

    Thread Starter New Member

    Sep 30, 2012
    12
    2
    SPQR: Those links were very helpful, thanks. I'd no idea the color codes were standardized. All of my electronics related experience comes from working for my assembly clients, Test Engineering departments at modern IC design and fab firms. The only iron transformers I've had to ID in the past were simple 4 lead step-down units. The info in those links will be invaluable considering my Father left me vintage tube transformers by the dozens.

    nsaspook: The codes are C300050 above the logo and 306017 below. I've entered them in google in myriad combinations and found nothing of use after hours poking around. All I can tell about it besides the brand and the numbers is that the core is 4.5" x 3.75", it weighs 6.72 pounds and is a horizontal enclosed mounting type with 11 wires. Once I've measured the outputs I may be able to ID it via the catalog you posted based on dimensions, weight, and outputs. Thanks very much.


    -Mike Bilan
     
  5. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    The copper wire winding enamel (insulation) can be deteriorated after some years which can cause fireworks. Be prepared.
     
  6. MicroMike

    Thread Starter New Member

    Sep 30, 2012
    12
    2
    Oh, I know. I was around for such fireworks when my Father tested a much larger transformer he found in a dumpster. Shame he didn't teach me more about these transformers, or that I didn't retain what he did, lol.

    Thanks for the tip anyway, though.


    -Mike Bilan
     
  7. The Electrician

    AAC Fanatic!

    Oct 9, 2007
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  8. crutschow

    Expert

    Mar 14, 2008
    12,984
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    A way to safely connect the mains power to the wires you suspect is the primary is to add a 120V incandescent lamp in series with the winding. If the winding is the primary, the bulb will not light or light only dimly. If the winding is not the primary (or there is a short), the bulb will illuminate relatively brightly but the bulb resistance prevents any fireworks.
     
  9. MicroMike

    Thread Starter New Member

    Sep 30, 2012
    12
    2
    Thanks for the tip! Any information that can potentially prevent my house from burning to the ground is as good as gold. :)
     
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    If that's the case, I recommend doing all testing on the concrete garage floor or in the driveway (I see California on the location, otherwise I would recommend the concrete basement floor).
     
  11. MicroMike

    Thread Starter New Member

    Sep 30, 2012
    12
    2
    I have a workbench setup in the garage with a half inch thick heat resistant soldering pad covering about half of it, roughly 4' x 6', that should do nicely. My Father left me a garage that's part electronics lab, part auto shop, and part machine shop. He spent most of his time out there prototyping a bunch of patents he filed when he wasn't out adding to his ever-growing mountain of surplus tools, instruments, and components.

    Despite the fact that it was and, in certain ways, continues to be something of an organizational nightmare it's left me pretty well equipped to safely test all the gear I'm attempting to sell off to cover my Mothers medical bills. The only things I'm really lacking in are knowledge and skills. I'm really glad I've found a place to seek these things out from others. Even at as-is prices I really hate the thought of selling someone an item that's useless or, even worse, potentially dangerous.

    So, many thanks to all who've replied and contributed to this ongoing endeavor. Your help is greatly appreciated.


    -Mike
     
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