[GreenKeys] 28 TD questions

Mon, 21 Jan 2002 12:50:58 -0700

Hi Jack:

At 01:58 PM 1/21/02 -0500, you wrote:
>...Before you get too worried about
>the pins...look very carefully to make sure the pins
>have not slipped below the plate and/or they're not blocked
>by dirt in the slots. Kinda unusual for them to be
>broken.

Hee-hee-hee-hee (insert big smile here)!  After a closer inspection of the
sense pin area, I found that the pins had indeed simply been pushed down
and off to the side of their guide slots.  I was able to easily pop them
back into position, and things seem to cycle fine now.  That was nice to find!

>The LXD runs on a normal 130VDC loop and the control solenoid
>should work on 110VAC...
>The rear connections should have the tape out/tape jam
>switch, the control solenoid and the mark (space)
>contacts. Easiest way to determine the mark/space
>contacts it to hook up a VOM and run a tape through (once
>you fix the pins, of course). I'm guessing that the three-pin
>connector is the signal generator's mark/space/common
>connections. They come from the small closed metal
>box in the machine. 

Yes, there is a metal can (that says "do not oil") which is the origin of
the cable that terminates in the 3-pin circular connector.  Hmm,
mark/space/common, so there is a separate switch contact for each?  I was
expecting a a simple open/close contact for keying the loop.  How does the
mark/space scheme usually hook up?  And how would you determine the
mark/space contact connections with a meter (or scope)?  Are these contacts
good to at least 150VDC?

BTW, pics are at (click on them to enlarge):  
http://www.vauxelectronics.com/gil/tty/gil-M28-TD.htm

>I don't have any military wiring
>diagrams, but the presence of the two terminal strips seems
>to indicate it's not overly different from a standard
>Teletype TD.

The lower terminal strip is just for 115VAC, but the upper terminal strip has:
1 - Wht     (cable-1)
2 - Blk     (cable-1)
3 - Shield? (cable-1)
4 - Shield? (cable-2)
5 - Wht     (cable-2)
6 - n/c
7 - n/c
8 - Blk     (cable-2)
9 - n/c

These cables go to the delta connector under the LXD.  I can trace these
connections out, but it would be handy if someone has a wiring diagram for
the LXD assembly and its delta connector.

>I'd recommend putting a resistor in series with
>the control solenoid just to be safe. There's always the
>possibility that it's a 48V coil.

Anyone know what coil resistance would be for the 48V and 115V coils?
Else, I can try 48V first (dc?) to see if it pulls in.

And what about some lubrication advice?

Thanks Jack!

gil

>Jack WA2HWJ
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]]On Behalf Of gil smith
>Sent: Monday, January 21, 2002 12:11 PM
>To: [email protected]
>Subject: [GreenKeys] 28 TD questions
>
>
>Hi folks:
>
>I have an M28 TD standalone unit (TT-603/UG) that I'd like to get working.
>I connected AC and the motor turns the mechanism just fine.  When I use a
>plastic rod to push the "run" solenoid gizmo, it feeds paper tape and I can
>see the sense pins coming out etc.  I have two problems though:
>
>First, I only see three of the five sense pins come up, so something is
>broken inside.  I have a spare LXD37 reader mechanism (serial 15!) that
>looks in decent shape, but I can't just swap the LXD out since the
>driven-shaft/gear portion is different.  I think I can either swap the
>driven-shaft parts, or the sense pins parts, whichever is easier.  Anyone
>have words of wisdom on dismantle and reassembly?
>
>Second, I have no documentation, so I am curious about the wiring.  There
>are two 9-position terminal strips inside.  The lower strip has AC
>connections for the line cord, internal power switch, and chassis ground --
>this was easy enough to figure out.  The upper terminal strip has
>connections to what appears to be two shielded-twisted-pair wires, with all
>six connections available.  These wires go to a delta connector underneath
>the LXD reader mechanism.  I presume one of these cables provides a
>low-voltage supply for the run solenoid, and the other one looks like it
>goes to a switch. Then there is what looks like another
>shielded-twisted-pair cable that is terminated in a 3-pin circular
>(mil-type) connector -- I presume this provides the data switch contacts
>for the loop.  I can likely figure this other stuff out as well, but if
>someone knows connection information, I'd appreciate it.  Specifically,
>what voltage does the run solenoid need, and what loop voltage are the data
>contacts rated for?
>
>thanks,
>
>gil
>

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