[GreenKeys] M19 Selector Magnet - magic smoke?

[Jim Cooper]

On 3 Aug 2021 at 18:19, John Thurmond wrote:

> Here's a picture of the selector mechanism: 
> https://photos.app.goo.gl/ru5dpLpdbVnT5WSE7
> vs. what I can see from the M15 Adjustments
> manual:https://photos.app.goo.gl/6rNUDeZz9qsaWxzj7

ah, first of all there are TWO different types of 
selector mechanisms:   the PULLING magnet, and 
the HOLDING magnet. 

your first photo is a holding magnet; 
the second drawing is a pulling magnet (note the long spring)

apparently the magnets themselves are different, 
because the M-15 manual I referred to in seeking 
info says the pulling magnet is M-177 with 105 ohms 
per coil; the holding magnet is M-207 with 92 ohms 
per coil.   Most important, the mechanical mechanism 
is different.

The pulling magnet makes the loop current create 
enough magnetic pull against the sprint to pull the 
armature against the magnet face; 

The holding magnet has a cam that PUSHES the 
armature against the magnet face, thus the loop 
current only needs to hold it there. 

> From looking at it, it looks like
> the best way to get at the coil is to
> remove the mounting screws for the
> magnet bracket, pull the magnet cores,
> and then replace the magnets. Is
> this correct? 

It's been decades since I worked on one, so 
without pulling one out and actually working 
thru it I would not feel confident to give step 
by step instructions !!   

However, take lots of pictures as you disassemble; 
to refer to a week later when you try to put it 
back together!   

Also, learned the hard way over the years -- when 
you remove screws put the screw back in the hole 
it came from as soon as you take off what it was 
holding.  That way, the screws don't get lost and you 
don't have to figure out which goes where later. 

[I'm copying my reply to the group, as some of the 
info might help others.]

Jim  w2jc