Info, spice model parameters for DEC pulse transformers?

Vincent Slyngstad v.slyngstad at
Wed Jul 18 08:39:13 CDT 2018

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.)


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