[GreenKeys] loop supply - part 2

[Virgil Bierschwale]

interesting.
guess I will need to RTFM as we used to say in the navy.
Luckily, I do have a set of manuals on hand.

I'm actually thinking about buying a known good lesu, BUT that is a lot of
wires to figure out <grin>

Thanks,

Virgil


On Fri, May 19, 2023 at 8:04 AM John, W9DDD <w9ddd at tapr.org> wrote:

> Good Morning Virgil
>
> Wondering how badly the LESU is messed.
>
> Perhaps it would be useful to describe how a unit would come from the
> factory.
>
> First both magnets are for the typing unit (the LP).
>
> They may be wired in series or parallel.  (for 20 or 60 mA)  (What is the
> value of those two power resistors wired in parallel?)
>
> Normally the wires go to the 20 pin connector on the printer and then out
> the mating connector to the A terminal on the bottom of the LESU.
>
> The selection of 20 or 60 mA connections are made on the A strip which
> unfortunately required inverting the LESU.  (why aren't the choices 30 or
> 60?)
>
> Then depending on whether there is a polar relay in the LESU, the selector
> magnet leads either go straight from the A strip to the C strip, (the one
> on the back wall of the cabinet) or through the polar relay assy and back
> to the A strip and out to the C.
>
> If you wanted to describe or send pictures of the LESU I could refer you
> to WD that was close.
>
>
> Those of use who mess with these things frequently have made up a set of
> test cables which bypass all the extra stuff.
>
> I inherited one KSR which had Bell System inside wire hooked directly to
> the keyboard contacts and a connector and shielded cable going to the LP.
> For some reason I assumed the connector was internally strapped for 60 mA.
> I ended up with a high resistance coil on one of the two selector magnets.
> I'm not sure if I got it that way or I damaged the coil because it ran it a
> fair amount that way until I started to restore the original wiring and
> realized I had a problem.
>
>
> I seem to recall you're down around Austin/San Anton area, kind of stretch
> for an in person consult, I'm on North side of DFW.
>
> On 5/19/2023 7:31 AM, Virgil Bierschwale wrote:
>
> Thanks to you folks, I now understand how the loop supply is wired in.
>
> The model 28 KSR I have has a LESU with no part number, and broken wires,
> things like that.
>
> So I want to wire the loop supply directly to the selector magnets (unless
> there is a better way).
>
> There are two selector magnets, so there are 4 wires.
>
> They appear to be orange, yellow, brown, and white.
>
> Any advice on how I should hook up the loop supply here?
>
> It's been a long time, but I'm assuming one selector magnet is for the
> typing unit, and the other is for the keyboard.
>
> My long time goal is to hook this up to an arduino so that I can send
> reports to it periodically.
>
> Thanks,
>
> Virgil
> N5IVV
>
>
>
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> --
> ---
> ----
> The above comments or recommendations are SWAG. Use at your own risk.
>
> John, W9DDD
>
>
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