[GreenKeys] Testing My Model 15 KSR

[Ralph Mowery]

----- Original Message ----- 
From: <WA5CAB at cs.com>
To: <john at johnmcclung.com>; <greenkeys at mailman.qth.net>
Sent: Monday, April 12, 2010 11:57 PM
Subject: Re: [GreenKeys] Testing My Model 15 KSR


> 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.
>


The Modle 15 series printers can not (atleast not well) run on a 20 ma 
circuit.  Either holding or pulling coils  can be wired to run on either 30 
or 60 ma.  If the two coils are wired in parallel then you run the printer 
on 60 ma if they are wired in series then you run the  printer at 30 ma.  I 
don't know where the 20 ma came from.  Maybe the computer printers that run 
on a 20 ma circuit ?

If possiable run the printers at 60 ma with the coils in parallel.  They 
will run slightly beter.  This has to do with the rise time of the current 
waveform.  Also the holding magnets work slightly beter for the same reason. 
Less inductance in the circuit.