Info, spice model parameters for DEC pulse transformers?

Vincent Slyngstad v.slyngstad at
Wed Jul 18 13:01:00 CDT 2018

From: Joseph Oswald: Wednesday, July 18, 2018 9:44 AM
> Thanks for the response. I had seen your info on the two other parts.
> Unfortunately, I have no idea if these system modules exist outside a
> museum.

You're welcome. 

I've seen them occasionally, but not often.  Like the flip-chip modules, I 
fear much of the information about the less common modules may not 
be recoverable.

> I might have to back off even further and work out a technique on
> something like the B301 or B611 modules, which seem to be obtainable
> and at least vaguely similar to the transformer circuits I am
> interested in.

Possibly quite similar, though with a lot less germanium and such, 
due to being of a later generation.

> Can you detail a little more what your measurement method is? Do you
> have an LRC meter or something, and measure the resistance +
> inductance open-circuit? At what frequency?

It has been a while, I'm working from memory, and not an EE to begin 
with, so I likely have the details wrong or at least a little fuzzy.

My understanding is that the gauge and length of the wire determine 
it's DC resistance.  An accurate resistance measurement in the milliohm 
range is tricky, as there are usually oxides, etc.  In theory, you can get 
a number that constrains the type and amount of wire in a winding.
There is an additional issue: sometimes your exemplar is actually
defective, so for the T2052, I tossed the measurements for the 
transformer that seemed atypical.  If you have at best one example, 
I guess you'll just have to hope the results are confirmed by the 

Measuring the inductance is a little easier, and as I understand things, 
much more important anyway.  Knowing the inductance and the core 
material, one can determine the number of turns.  I use a tool called 
"mini Ring Core Calculator" by Wilfried Burmeister to explore the 
likely possibilities.  Knowing or postulating an FT-37-77 core constrains 
the problem nicely.  For the actual measurements, I borrowed a friend's 
inductance meter.

Your emphasis is not really on physically re-creating the part, so it 
seems likely that all Spice really needs is the inductance of the 
windings and some simple assumptions about their coupling.


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