[GreenKeys] Connecting a Model 14

[John Nagle]

On 08/11/2014 11:52 AM, greenkeys-request at mailman.qth.net wrote:
> Message: 33 Date: Mon, 11 Aug 2014 03:12:58 GMT
> From:"airrelic at juno.com"  <airrelic at juno.com> To:dnewman at gmail.com
> Cc:GreenKeys at mailman.qth.net Subject: Re: [GreenKeys] Connecting a
> Model 14? Message-ID:<20140810.231258.13482.1 at webmail01.dca.untd.com>
>  Content-Type: text/plain; charset="windows-1252"
>
> Well, it's a
> relay.http://www.lintechcomponents.com/product/011680205/22800156111/31951
>
>
It's rated for 6 volts, and it's my guess that some clever person
> rigged it up to be keyed by a computer. Looks like the relay drives
> the power supply which in turn drives the selector magnets. If it
> were me, I would check to see if the unit still functioned, no stray
> voltages or unintentional grounds, or anything that would hurt the
> teletype or my computer. Then, by studying the schematics on John
> Nagle's site I would fashion a connector to use the serial port on a
> pc.http://www.aetherltd.com/connecting.html  That should satisfy the
> hardware requirement. Then you need a program to drive the teletype.
> Heavy Metal or MMTTY? I have no experience with these and maybe
> someone else might jump in here. You have to be able to adjust the
> program to make the machine happy, flip or reverse the signal etc.

     Right.  It looks like a loop supply and a relay.

     My guess, given the vintage, is that it's intended to be
driven from a classic RS-232 serial port.  If you have
an older desktop computer with a serial port, DOS or Windows
will, if set to 45 baud, 5 bits, no parity, 1.5 stop
bits, send the right output for a Teletype.  Heavy
Metal can run that.  So can my "baudotrss".  With a modern
computer, you'll probably need a USB to serial converter,
although it might actually need the 12VDC of older serial
ports.

     Be cautious. You have 120VAC, 120VDC, and a computer
interface in a circuit that hasn't worked in years, has
no strain relief on the power cord, uninsulated components
in the open carrying line voltage, fragile design,
and no sign of a fuse.  This isn't modern no-voltage-bigger-than-12V
electronics.

    Check with an ohmmeter that nothing is
connected to anything it shouldn't be.  There should be infinite
resistance between both sides of the power cord and both side
of the selector magnet, and infinite resistance between both
sides of that 1/8" plug and both sides of the power line.
Plug it in through an outlet strip with a breaker and a GFCI, and keep
hands away when energized, please.

    Function check - power up this loop supply, then apply 9V battery to
1/8" plug.  Relay should trip and selector magnet should move.

    If that works, all you need is a desktop PC, a 1/8" socket, and
a DB-9 connector (Pins 3 and 5 on a DB-9 are transmitted data).

			John Nagle