[GreenKeys] Many Questions about 28 RO TTY

[ad7i]

Thanks to all those who provided info about the vertical tab feature of my
28RO.  I have some additional questions that I hope people can help with.

Let me recap the background of my 28RO. My 28RO came from an architectural
or engineering firm in or near NYC. I'm fuzzy on the details but here's
what I recollect.  The TTY was probably abandoned in place and sat in that
office for a number of years, idle and unused.  When the company moved to
new office space in the mid 1990s I was given the printer via a friend of a
friend.  When I received the 28RO I found it to be clean, with simple
wiring inside.   I tested it with a DOS PC RTTY program and the TTY worked
well, geared for 75 WPM. I then did nothing else with and and it has been
stored in my dry basement, unused for 20+ years.

My project for this winter is to get this printer (and my Model 15) in good
working order again and put them to some serious use.  My fantasy is to
eventually write a program for a Raspberry Pi that would automatically
scrape some internet news sites on a daily basis for items of interest to
me and then send selected articles to the TTY for printing when I'm in my
workshop.  Until that's operational I'll use them mostly to copy W1AW, ITTY
and 518 kHz NAVTEX (until that's gone).

Below are some photos of the unit that are related to my text below:

Cabinet Exterior (typing unit removed):
http://ad7i.net/docs/tty/m28ro-cabinet-exterior.jpg

Terminal Strip (partial):  http://ad7i.net/docs/tty/m28ro-terminal-strip.jpg

Paper Roller Switch:  http://ad7i.net/docs/tty/m28ro-roller-switch.jpg

Stunt Switch??:  http://ad7i.net/docs/tty/m28ro-stunt-switch.jpg

And a pictorial of the cabinet wiring, as I determined by visual inspection
and with a continuity tester:

     http://ad7i.net/docs/tty/M28RO-Cabinet-Wiring-191011-01.pdf

In going through the lubrication document (
http://www.navy-radio.com/manuals/tty/226B-5504.pdf ) I find that some of
the document pictorials match my printer exactly, while others I just can't
seem to match a pictorial in the document with my actual hardware.  For
example, on page 3-8 I see where detail 5.06 is located on the typing unit.
But when I look at the pictorial at the bottom of page 3-8, I don't see on
my typing unit anything in the area of 5.06 that closely matches the
document pictorial at the bottom of page 3-8.  Seeing that the manual was
created in 1955, I wonder if my typing unit is a later model, and the
hardware "changed" over the years. Absent my ability to match pictorials to
hardware, I'm taking the approach of lubing anything that looks like it
might move.   But I do worry that I'll miss some key area for lubrication,
run the printer for lots of hours which then causes something to "break",
with no way for me to fix it.

Question:  Is there a way to "date" my typing unit from looking at it?  I
don't see a serial number.  Were a number of changes made to the typing
unit over the years?

Question:  Is there anything in the typing unit that requires disassembly
(other than removing the typing unit from the cabinet) in order to properly
lubricate the typing unit?

Question:  Is it safe to set the typing unit on its side (right side on the
bench or left side on the bench)?  The lubrication document implies that
it's OK, but I don't see what the safe resting points would be.  It looks
like the typing unit might rest on delicate hardware if it was placed on
its side.

I've carefully gone through the cabinet wiring, to see what's connected to
what.  The wiring seems to be very minimal, and somewhat unorthodox (zip
lamp cord used for wiring to the motor, Sonalert and aux alarm lamp), but
what is there is very neat and orderly.  You can see a portion of the
cabinet terminal strip on one of the photos above.

In looking at the PDF of the cabinet wiring, it looks to me like there was
the provision for a visual (lamp at terminals 32 & 33, this lamp sits in
the red plastic cover on the front right side of the cabinet) and audible
(Sonalert at terminals 29 and 33) for a NO PAPER condition.  There is no DC
power supply in this system, but if a 12 VDC power source was connected to
terminal 30 (positive) and 33 (negative) and a strap added between
terminals 31 and 32, then when a NO PAPER condition occurred (and SW2, in
the cabinet where the paper enters the cabinet, was closed), then the
Sonalert would sound and the lamp at terminals 32 & 33 would illuminate.
SW2 would allow the Sonalert to be disabled.  The lamp is somewhat odd in
that's it's a physically small incandescent lamp with the tubular bulb,
with the glass bulb being 0.2" in diameter and 0.35" in length.  There are
two pigtails extending from the lamp base (lamp not designed to be used in
a socket) that are spliced to black zip lamp cord (splice wrapped with
electrical tape in sort of an untidy way, the only thing that's untidy
inside the cabinet) that are connected to terminals 32 and 33.  There is no
continuity between terminals 32 and 33, so I assume the lamp is blown
(although it could be faulty wiring at splice between the pigtails and the
black zip lamp cord).

Another other unusual thing is that there appears to be stunt box on the
back of the typing unit.  It's very hard to see because there is a paper
tray for the sprocket feed paper that makes the area of the stunt box hard
to see (see photo).  There are two electrical wires on contacts that appear
to be controlled by slot 29 and another pair of electrical wires on
contacts on slot 30.  These wires go to the connector on the right side of
the typing unit.  I tried to see to which pins on the typing unit connector
these four wires were attached, but the sleeving over the wire contacts on
the stunt box is so tight and complete that I can't get a probe in there to
check continuity.  The wiring to the stunt box contacts is so nicely done I
assume that this was done at the factory, and not an after-install add-on.

Another unusual thing is that there is a micro-switch on a lever near the
right side of the paper roller (see photo above).  This too appears to be
wired to the connector on the typing unit.  I haven't tried to see to which
pins this micro switch is attached to the typing unit connector.

What I do know is that the loop circuit attaches to pins 0 and 1 on
connector that is attached to the cabinet terminal strip and that pins 12
and 13 are connected to the cabinet terminal strip to pins 31 and 30
(respectively).  What I don't know is what on the typing unit connects to
pins 12 and 13 on the typing unit connector (which is wired to be in
parallel with the back of cabinet microswitch that closes during a NO PAPER
condition).  Are pins 12-13 connected to the micro switch near the right
side of the paper roller, or perhaps one of the sets of contacts on the
stunt box.  I don't know at this point.

Question:  Any insight into the function of the microswitch near the right
side of the paper roller?  Is this a secondary NO PAPER switch?

Question:  Any insight as to what the electrical contacts on the stunt box
at position 29 and 30 might be used for?  Could those contacts be wired to
pins 12 and 13 of the typing unit connector, so that a remote operator
could also cause an audible and visual alarm at this TTY?

I had mentioned in a prior message that my copy lamps did not work.  I've
found that was due to operator error.  The switch was in the center (off)
position.  When I move the switch to either NORM or MAINT the copy lamps
work as expected.

Question:  Page 2-2 of the adjustment and lubrication document (URL above)
shows the typing unit tilted forward in the cabinet.  Is that tilting
feature supported by ALL model 28 printers or only some 28 printers?    I
don't see where mine is hinged in the cabinet or what I screws I would
remove to allow the typing unit to tilt forward while in the cabinet.  I
don't think my cabinet supports this tilting feature

Question:  On page 3-2 of the adjustment and lubrication document it shows
two types of screws.  I'm missing two of the screws shown at detail 4 and
one of the screws shown at detail 5.  Are there any functionally equivalent
screws I might use as replacements?

Thanks for your time and consideration.

73, Paul Newland, ad7i
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