Looking for PDP-8 G603 "Memory Selector Matrix" boards (or dec T-2052 transformers)

Vincent Slyngstad v.slyngstad at frontier.com
Thu Apr 13 17:36:17 CDT 2017

> I realize it's a long shot, but does anyone have:

> - Any spare T-2052s (or know of a source)
> - Any idea what the T-2052 *was* so I can try to replace them.  I haven't
> found much detail as of yet.

Good news on this front!

I had previously obtained a data sheet for the T2037, a similar transformer.

I extracted 4 each T2037 and T2052 from a broken G228, and today I was 
able to get measurements off of them:

A: 230uH, 170 mohm primary, 42.9uH 100 mohm secondary
B: 220/170, 41.6/100
C: 232/170, 43.8/60
D: 231/170, 43/80

These are consistent with 16 turns and 7 turns of #33 wire, wound on 
an FT37-77 toroid per the instructions on the data sheet, and also with 
the 220 uH /43 uH 20% specs that appear there.

Here are the T2052 measurements:
A: 597/320, 597/320
B: 530/270, 530/270
C: 34/1040, 24/680
D: 551/280, 551/280

Ignoring "C", which is quite likely broken in some way, these are 
consistent with a 25 turn 1:1 transformer.  I'm not sure what they 
are wound with, as #33 wire should give a lower DC resistance.
(#34 is closer.  It's also possible that they changed cores, but I 
suspect that they are also wound on FT37-77 cores.)

It's possible that a fairly standard modern 1:1 pulse transformer 
could be substituted.  The 78615/2JC, for instance is 500uH, 1:1 
if you ignore the center tap pins.


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