[GreenKeys] Testing My Model 15 KSR

[WA5CAB at cs.com]

John,

To add to or comment on what's already been posted, relatively few Model 
14/15/19 will run on 20 mA.  That requires different magnets in what's called 
a "Holding Magnet" selector.  The majority come with a "Pulling Magnet" 
selector.  You can tell the difference by the fact that the pulling magnets are 
cylindrical and the holding magnets are rectangular in cross section.  I've 
had in my lifetime maybe 30 14's or 15's and only about two had holding 
magnets.  However, the first M15 I ever had (in 1962) had holding magnets.  So 
they do turn up.  But both of the ones I recall having had a selector toggle 
switch, too.  I can't certify that all did.

You can't rewire a pulling magnet selector for 20 mA.

If you do not disconnect the wires actually going to either coil, you will 
not accidentally get them wired so that they buck (oppose) each other.

Hooking the local keyboard and selector magnets in series with the local 
loop supply (with dropping resistor adjusted to set the resting current to 60 
mA) creates what's commonly called a local loop.  Typically used for testing 
and generating local hard copy.  You can jack a TD or keying generator into 
the loop and run a FOX tape and check and adjust range.

In a message dated 4/12/2010 9:10:41 PM Central Daylight Time, 
john at johnmcclung.com writes: 
> After I get my Model 15 KSR all cleaned and lubricated but before I
> build the RS232 interface, can I test it by just connecting the selector
> magnet, keyboard, limiting resistor and power supply in series?
> 
> Regulated +120VDC => 2K 10W resistor => keyboard => selector magnet =>
> -120VDC
> 
> Does keyboard or selector magnet polarity matter?
> 
> John 
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480