From: spam@spam.com   
      
   On Sun, 28 Oct 2012 16:29:16 +0100, "GRe"   
    wrote:   
      
   >   
   >"Phil Allison"  wrote in message   
   >news:aes634Fhmh9U1@mid.individual.net...   
   >>   
   >> "GRe"   
   >>   
   >>> Winding W1:   
   >>> Rdc = 32ohm   
   >>> Saturation at about 50V, W2 open   
   >>> Inductance 8.82H @ 10V/50Hz   
   >>> Inductance 6.58H @ 10V/100Hz   
   >>>   
   >>> Winding W2:   
   >>> Rdc = 29ohm   
   >>> Saturation at about 37V, W1 open   
   >>> Inductance 5.36H @ 10V/50Hz   
   >>> Inductance 4.11H @ 10V/100Hz   
   >>>   
   >>> Winding ratio N = 1.34   
   >>> Impedance ratio = 1.79   
   >>>   
   >>> F-response -3dB @ 27kHz with a 600ohm load on W2   
   >>>   
   >>> +3dB @ about 80kHz with (almost) no load on W2   
   >>> +22dB @ 186kHz resonance with (almost) no load on W2   
   >>>   
   >>> Iron lamination dimensions 48x40x20mm   
   >>> It's "tarred" and has NO airgap   
   >>> Beside end taps, no additional taps on W1 and W2   
   >>>   
   >>> What could the purpose have been?   
   >>> Anybody any idea???   
   >>>   
   >>   
   >> ** Almost certainly it's a high quality, 600 ohms line driving   
   >> transformer.   
   >>   
   >> The primary impedance is about 1000 ohms and so suits cathode drive from a   
   >> small power tube, via a coupling capacitor.   
   >>   
   >> Max operating level is about 10 volts rms, with 13 volts drive on the   
   >> primary.   
   >>   
   >> Line receiving versions were usually fitted into a ( mu-metal) shielding   
   >> can.   
   >>   
   >>   
   >> ...  Phil   
   >>   
   >>   
   >   
   >Sounds like a bull's eye shot to me!   
   >With a line transformer application in mind I did some more tests.   
   >   
   >Inductance at -20dB steps:   
   >8.8H @  10V/50Hz (XL= 2.8Kohm)   
   >3.4H @ 1.0V/50Hz (XL= 1.1Kohm)   
   >1.6H @ 0.1V/50Hz (XL= 500 ohm) Z-total about 450ohm   
   >0.9H @ 10mV/50Hz (XL= 280 ohm) Z-total about 270ohm   
   >   
   >2.4H @  10V/1kHz (XL=  15Kohm)   
   >1.2H @ 1.0V/1kHz (XL= 7.5Kohm)   
   >0.9H @ 0.1V/1kHz (XL= 5.6Kohm)   
   >0.5H @ 10mV/1kHz (XL= 3.1Kohm)   
   >   
   >Looks like impedances are OK with a possible exception for 50Hz/.1V/10mV   
   >where XL parallel to the reflected 600ohm termination are lowish, about 450   
   >& 270ohm.   
   >Would this imply a lower-R termination for more constant Z to the driver?   
   >   
   >Is a lowish impedance at low frequency & voltage of much significance   
   >regarding the low output impedance of a cathode follower/driver?   
   >   
   >   
   >Square wave test, Vi= 10Vpp/10kHz:   
   >Rise time at W2 = 14µS with a 600ohm load   
   >Rise time at W2 = 2µS with a 3600ohm load   
   >   
   >Square wave test, Vi= 10Vpp/50Hz:   
   >W2 droop about 7% at the trailing edge vs. leading edge, 600ohm load   
   >W2 droop also about 7% at the trailing edge vs. leading edge, 3600 ohm load   
   >   
   >Because of the 14µS rise time with 600ohm load, while without load   
   >significant ringing is present I wondered if a higher resistance would do   
   >better.   
   >Optimum was found with a 3600ohm load, almost no over- or undershoot.   
   >With the 3600ohm load the -3dB point shifted to about 175kHz.   
   >Would this imply a higher-R termination for a better signal transfer?   
   >   
   >   
   >Does the above data confirm application as a 600ohm line driver or does it   
   >suggest something else?   
   >   
   >Regards & TIA,   
   >Gio   
   >   
   Could you explain these tests in a little more detail? I'm not sure   
   why the inductance appears to be dependent on the voltage.   
      
   d   
      
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