Tandy Professional Forum   Section: Model 1 / 3
Subject: Funny 6-pin DIN   Total messages: 8
============================================

#62473   3 Replies   09/16/96   21:06:17
From: Richard A. Cini, 70153,3367
To:   All

Hello, all.

     As I am cleaning-up and restoring my two Model Is, I've
noticed something. One keyboard unit (16K Level II) and one
expansion unit have a 6-pin DIN connector hanging out of it.
Obviously some sort of modification. Has anyone seen this
before??

     I still have to open the units and trace the connections. I
just got the original service manual for the keyboard unit, so
off I go...

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#62477   Reply to #62473   1 Reply   09/17/96   11:08:13
From: David J. Campbell, 72707,1346
To:   Richard A. Cini, 70153,3367

Rich,

   That was the famous "twisted pair" mod, done by Radio Shack to
improve reliability.  It goes to a mating connecter grafted onto
the expansion interface.  I forget now which cable from th CPU to
EI is used with this mod - the straight or the buffered.  (it's
been a lot of years)  Perhaps someone else can jump in here-

                                   Dave


#62479   Reply to #62473   09/17/96   17:18:05
From: Frank Gottschalk, 72623,40
To:   Richard A. Cini, 70153,3367

Yes Richard, I've seen those DIN pigtails before, but not sure
what they're for. May have something to do with the later
improvement of buffering between the two units. I remember it
with the buffered cable too.


#62490   Reply to #62477   1 Reply   09/18/96   21:36:27
From: Richard A. Cini, 70153,3367
To:   David J. Campbell, 72707,1346

David:

     That seems to make sense:  the signals duplicated are RAS*,
CAS*, and MUX. I guess that there was a problem with these CPU
signals reaching the EI.

     The problem now is that I'm trying to switch EIs: I have
one good one (without the mod) and one bad one (the one without).
Naturally, the boards are different revisions. Do you know if the
mod paralleled the edge connector signals??

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#62493   Reply to #62490   1 Reply   09/19/96   13:13:10
From: David J. Campbell, 72707,1346
To:   Richard A. Cini, 70153,3367

I imagine the mod cut the signals at the edgecard and routed them
through the new cable as 3 twisted pairs.  I haven't set up and
run any of my model 1's in at least 5 years, so I'm not really up
on it any more.  Unfortunately, all my old TRS80 stuff is in
storage 1500 miles away.

                    Dave


#62500   Reply to #62493   09/21/96   12:42:21
From: Richard A. Cini, 70153,3367
To:   David J. Campbell, 72707,1346

Dave:

     Seems to make sense, although I never opened up the EI
buffer to see what was up.

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#62502   Reply to #62473   1 Reply   09/23/96   00:16:18
From: Howard Sommerfield, 75247,2061
To:   Richard A. Cini, 70153,3367

The connectors were to bypass part of the buffered cable, those
machines would just hang hang up at the slightest provocation.
you will need a mate to it or some expertise to undo it if you
have a non buffered Expansion Interface

Howard Sommerfield


#62503   Reply to #62502   09/23/96   19:09:19
From: Richard A. Cini, 70153,3367
To:   Howard Sommerfield, 75247,2061

Howard:

     Thanks for the info. Really what I need now is a schematic
for the EI. I have two EIs with two different board revisions, so
it'll be hard to transfer the connector.

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