[GreenKeys] M19 restoration

[gil smith]

Hi Jan:

Sounds like you are having fun with that M19!

I have worked on a couple of 15s, but guys like Jack or Jim or Don have the 
real insight to your 19.  A few notes are scattered below:

At 08:35 PM 11/14/2004, you wrote:
>Here are some things that I have learned about the 19 set this week:
>
>The gear on the far right end of the horizontal shaft is marked 74913.  The
>gear on the motor (synchronous motor) is marked 74912, and the gear on the
>keyboard shaft is numbered 74595.  All this makes me think that the 
>machine will
>work at 60 wpm.

Sync motor is good.   My 15 parts book is still packed somewhere, so I 
can't look up gear numbers at the moment, but whatever the actual speed, 
you can easily talk to it from a pc or radio.  Your machine is likely 
geared to 60-wpm, though it may be 66.  I have heard something about 
available 75-wpm gears, but I also heard that the machine self-destructed 
shortly after installation.


>Here is a long one.  The terminal block seen from the back and above the
>selector square core HM magnet has three strips and six screws (no 
>switch).  The
>center two are not used.  An orange and black wire goes to the lower left 
>screw
>and a red and black wire goes to the lower right screw.  Two resistors are
>placed across the top outer screws, but they don't add up to 5000 ohms.  I am
>sending a picture to Gil showing this wiring configuration.  The question 
>will
>be: Do I need to set the HM up for series or parallel, to provide 30 or 60 
>mil
>operation?

One of my two M15s has this "holding magnet" design, with the mags in 
parallel for 60-mA use.   My coils are paralleled on the left and center 
terminals on the small terminal strip.  From the angle I could see it, I 
could not tell whether a resistor is wired across the coils, or not.  I 
will need to dig it out to remove the terminal cover plate.

It looks like your holding-mag machine also has the mags in parallel, and 
has a resistor across them on the terminal strip.  What value (or color 
code) is that resistor?  I'd say you have a 60-mA setup, which is the way 
to leave it.


> >From what I can tell the Polar Neutral Key and wiring has been removed.  I
>also think the polar relay has been removed.  The pictures that I send to Gil
>will confirm this.

Well, my second M15 has the other "pulling" sel-mag design, with round 
coils.  This unit was wired for a polar relay.  The relay plugs sideways 
into a socket mounted on a metal tower in the rear corner of the 
machine.  I bypassed all this wiring to isolate just the selmags and 
keyboard contacts.

Your machine is different.  In the place where this little metal tower sits 
on my machine, you have just a relay (actually, it looks more like a 
solenoid and switch contacts).  This relay of yours does not look like it 
has small high-speed contacts, so I am not sure whether this could be a 
polar relay for the line, or contacts for some other function.  The polar 
relays I have seen have smaller contacts and are sealed in a removable 
enclosure.

Other than that relay, you have a fuse block and power resistor in the back 
-- these are the same in my machine.


>Here is a good question: I keep hearing the phrase "polar magnets."  There is
>a shaft going from front to back of the keyboard behind the keys.  This is
>the one with the gear at one end labeled 74595.  Now this shaft spins what 
>the
>book calls the transmitter mechanism.  When you push a key, this shaft and 
>odd
>collection of washers spins and stops.  Now, does this thing make the pulses
>in much the same way as the TD reads the tape and makes pulses.  Is this 
>think
>the "polar magnets?"

That shaft gizmo serially keys the bit pattern out the line contacts when 
you press a key.  Both the keyboard and TD get a parallel code (encoding 
bars or a row of holes), and convert it to serial data (a timed sequence of 
line-open or line-closed bits) for sending on a neutral loop, or activating 
a polar relay.

I presume "polar magnets" is referring to a polar relay.  Polar stuff was 
optional, for long-line use.


>I have printed out and put together several wiring diagrams.  Using colored
>pens, I have outlined the loop as it goes through the components.  I am 
>sure it
>will get clearer, but would the terminal unit and power supply be plugged
>into the machine through the original phone female receptacles behind the 
>table
>and on the power plug in strip with all the odd receptacles?  I am a little
>lost as to where to start the loop.  I would like to keep the TD and the 
>keyboard
>in the loop. All the factory wires are in place.  If they had been all cut
>from the printer, the loop would seem easy, I guess.

I don't know anything about the model 19 table wiring.  Anyone?


>I have been reading the sections on RTTY in my Ham Radio hand books, the
>older versions.  I have a Heath Kit B+ regulated power supply from the 
>60s.  With
>a resistor, I think it would work as a quick test, loop power supply.

For what voltage and current is this supply rated?

A loop supply can be current-source design, but it is usually comprised of 
a high-voltage source, and a series-connected, suitably sized power resistor.

For example, many designs use 120VDC in the loop supply -- this requires a 
series-connected current-limiting resistor of:
120 VDC / 0.06 Amps = 2000 Ohms (2K).
Note that the voltage source must be able to continuously supply at least 
60-mA.
The resistor will need to dissipate:
120 VDC x 0.06 Amps = 7.2 Watts.
A resistor of a least 10W rating needs to be used, and it needs to be 
mounted to a heatsink of sorts to dissipate the heat.

A loop is nothing more than this voltage source and resistor connected in 
series with tty gear.  The tty part of the loop can be a simple connection 
to selmags for a printing-only loop.  Or, you can add keyboard and td 
contacts, wired in series, so you can also send on the loop.

Oh, and that box on casters you have seen in M19 pics is, IIRC, an optional 
ROTR (receive-only-typing-reperforator).  This punches tape and types on it 
as well, from the line (ie: it has selmags).

let us know your progress ,

gil


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