Info, spice model parameters for DEC pulse transformers?

Joseph Oswald josephoswald at
Wed Jul 18 11:44:19 CDT 2018

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

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.

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?


On Wed, Jul 18, 2018 at 9:39 PM, Vincent Slyngstad
<v.slyngstad at> wrote:
> From: Joseph Oswald: Wednesday, July 18, 2018 12:15 AM
>> I'm trying to model the PDP-1 DEC system models, first with SPICE
>> (ngspice on Linux), then with VHDL.
> The spice modeling of flip-chip modules has been an interest area for me.  I
> imagine that's similar, though perhaps less daunting, than modeling the
> earlier system modules.  Flip chip schematics, etc. can be found here:
> and some of the spice model stuff here:
> Particularly a parts library and the Perl to extract information (netlists)
> from the Eagle schematics.  There are sub-directories with results from the
> Perl for red and blue handled modules, and a few of the green.  Finding data
> to fill in the component model library is "fun",
> as the parts are long obsolete, and data sheets are hard to find.
> I also lack the EE skills to be effective at converting the data sheets into
> spice models, even when I can find them.
> Your first "fun" step might be to locate module schematics and convert them
> to a useful form.
>> I'm struggling to understand the properties of various transformers in
>> the system module circuits, most importantly (at least, the ones I see
>> in schematics I want to model)
> Those are all earlier than the info that I have, which is mostly for the
> T2037 and T2052.  Perhaps the earlier ones are wound on a similar core, or
> the measurement technique Josh and I used can be used to begin to reverse
> engineer them:
>> Is there any source for information about these? Basic specs? I don't
>> even know what the turns ratios are for these parts, much less
>> plausible inductances, so my spice models misbehave pretty badly.
> Unfortunately, the schematics don't usually state the relevant specs
> (just part numbers), so it may be necessary to measure up originals.
> (Hopefully in-circuit.)
>    Vince

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