Received-SPF: none (domain of classiccmp.org does not designate permitted sender hosts)
Message-ID: <A5E82F5AF844488E8EB84704F7F57646@Vincew7>
To: "Josh Dersch" <derschjo@gmail.com>,
 "General Discussion: On-Topic and Off-Topic Posts" <cctalk@classiccmp.org>
References: <CADBZjLZL7h1N-Wxb-PodmzPmrshTuode1XMhVxezdZzaQVeumQ@mail.gmail.com>
In-Reply-To: <CADBZjLZL7h1N-Wxb-PodmzPmrshTuode1XMhVxezdZzaQVeumQ@mail.gmail.com>
Subject: Re: Looking for PDP-8 G603 "Memory Selector Matrix" boards (or dec
 T-2052 transformers)
Date: Thu, 13 Apr 2017 15:36:17 -0700
MIME-Version: 1.0
Content-Type: text/plain; format=flowed; charset="UTF-8"; reply-type=original
Content-Transfer-Encoding: 7bit
Importance: Normal
Precedence: list
From: Vincent Slyngstad via cctalk <cctalk@classiccmp.org>
Reply-To: Vincent Slyngstad <v.slyngstad@frontier.com>,
 "General Discussion: On-Topic and Off-Topic Posts"
 <cctalk@classiccmp.org>
Errors-To: cctalk-bounces@classiccmp.org
Sender: "cctalk" <cctalk-bounces@classiccmp.org>
Content-Length: 1344

> 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:

T2037:
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.

    Vince