[GreenKeys] Rebuilt M15

[John Nagle]

>>> From: "Bob & Linda"<lrsmith at cableone.net>
>>> To:GreenKeys at mailman.qth.net Subject: [GreenKeys] Rebuilt M15

> It's almost ready to start testing...need to adjust the carriage
> return spring tension and dashpot.  But for the first time in
> decades, it's now running under its own power :).  I ran it for a
> little while both while holding the selector magnets closed and also
> just letting run open for a minute.  Keyboard transmitter seems to
> work fine.  Rest of the machine chugs away like a steam tractor lol.
> After I get the carriage return straightened out, I need to start
> figuring out the whole loop supply/communication thing.  If I get a
> power supply, I can at least put they keyboard in the loop and work
> the bugs out that way before sending it anything more complicated.
> Also tried hooking up my '50s vintage TU to it...fed it a signal
> from the computer, but didn't get any response from the selector
> magnets, so I'm guessing there's probably some component in it that's
> failed in the past 60 years.  Bummer.  So, working on other plans
> now...

You should see 55 ohms (or 220, if the magnets are wired in series)
across the selector magnet and across the input plug for the
typing unit.  There's nothing between those two points except
contacts and bypass caps.  Any electrical problems should
be resolvable with an ohmmeter.

A good first test is to attach a small 9V battery directly across the
selector magnet and see if it will pull in.  If that works, try
applying the 9V battery to the input jack for the typing unit,
which is normally connected to terminals 45 and 46 for direct
connection to the selector magnet.
This should be enough to stop "running open".  You can't really
run the machine on a 9V battery, but it's enough to pull in the
selector magnet.  Don't leave 9V on there for long without
measuring the current.

				John Nagle