[GreenKeys] Of current loops and voltages.. (M15 20mA / 60mA)

[WA5CAB--- via GreenKeys]

Bill,

I think my original comment only went to you direct because of the way that 
the Greenkeys list is set to obey the REPLY and REPLY ALL commands.  REPLY 
only goes to originator and I am forever forgetting that on Greenkeys.

The 14/15/19 sets in later years could be had with one or the other of two 
types of Selectors, Pulling and Holding.  Pulling (with the big black 
cylindrical magnet coils) are by far the most common.  A machine with Pulling 
magnets can only be used on a 60 mA loop.  The two coils are already in series.  
The holding magnet selector has smaller square coils, in parallel for 60 mA 
and in series for 20.  The difference, besides the coils, is that the 
holding magnet selector has a cam that mechanically presses the armature against 
the magnet poles 6 or 7 (I've forgotten which) times per revolution.  If the 
bit is a Mark, the magnet holds the armature against the pole long enough 
to set that bit as a Mark.  If the bit is a Space, the armature moves away 
from the magnets and the bit is set as a space.  The pulling magnet selector 
pulls the armature for a Mark and doesn't for a Space.  The pulling magnets 
generate a much strong magnetic field but that takes much more power (((3X 
apparently).

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

In a message dated 09/15/2015 08:34:18 AM Central Daylight Time, 
drlegendre at gmail.com writes: 
> But I wasn't aware of the SS magnet driver circuit in the M33 and 
> similar. I was also puzzled over the 20mA mode on the M15, which with 4X 
> inductance seemed to me would seriously impede the cycle time if still being driven 
> with 120V. Apparently it does slow things down, but not so much that the 
> machine won't function. From the sound of it, it's a power-saving compromise 
> intended for use when multiple machines are installed in somewhat close 
> proximity. 
> 
> 
> Best,
> Bill
> 
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20150915/5cf3b2b7/attachment.html>