Author Topic: Redesigned prepay 3-slot electromagnet  (Read 490 times)

Offline Stan S

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Redesigned prepay 3-slot electromagnet
« on: January 21, 2017, 01:02:01 PM »
If you work on enough 3-slots you'll eventually find strange changes that Western Electric made to them. Below is a picture of a prepay cointrack with a redesigned electromagnet. Why after 30+ years of using the standard electromagnet Western would devote resources to redesigning it is hard to figure out. I have never been able to find any documentation on the newer part.
Stan S.

Offline trainman

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Re: Redesigned prepay 3-slot electromagnet
« Reply #1 on: January 22, 2017, 01:58:44 AM »
I remember reading in a BSP about the magnet. It was done for some circuit modification. I cant recall where, and so far i havent found where i saw that information.

Offline RotarDad

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Re: Redesigned prepay 3-slot electromagnet
« Reply #2 on: January 27, 2017, 10:55:43 PM »
I found this new electromagnet.  In BSP 506-100-106 from Nov '70, this item is described.  This BSP relates to updating 3-slots to dial-tone first and the Automatic Nickel Local Overtime Feature.  The Nickel Local Overtime feature requires the D-180352 kit.  This pic is from that BSP, but I first found the pic in Ron Knappen's Payphone History on p.220.  There seems to be an extra wire from the electromagnet down to terminal A on the chute.  Stan, can you explain how this might have worked?
« Last Edit: January 27, 2017, 11:01:53 PM by RotarDad »
Paul

Offline Stan S

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Re: Redesigned prepay 3-slot electromagnet
« Reply #3 on: January 28, 2017, 10:10:15 AM »
Paul
Good work on digging out the BSP. Strange that I never noticed the reference in Ron's book.
 
There are 4 wires in total on the coin track. The same as with the older style electromagnet. Two green from the magnet and two brown from the coin microphones.

I'm fairly sure I know why the first nickel coin trap release was moved from the right side of the electromagnet arm to the left side. It's a little hard to explain but I'll do my best.

As the 233s, 234s and 236s aged, the coin release buttons corroded and collected dirt. When the button was pushed if it hung up and didn't spring all the way out, the coin track didn't return to its resting forward position and the spring loaded assembly on the back of the track didn't fully snap shut (see attached). That left a space between the spring loaded assembly and the bent tip of the arm of the trap release lever connected to the electromagnet. The next nickel that was deposited got caught in that space. When an attempt to release the nickel by pushing the coin release button was made, the tip of the arm of the release lever was pushed back, out of the hole in the track. Eventually the arm would bend back and any nickel deposited would get caught between the bent tip of the arm and the spring loaded assembly. From that point on the coins would just keep piling up in the coin track. I've gotten payphones where the nickels were so jammed in the track that I had to use a screw driver and pry them out.
By eliminating the arm and releasing the coin trap on the left side (by pushing the tab on the nickel trap) that problem was eliminated.
Northern Electric solved the problem by modifying the standard electromagnet. The short arm pushed the tab on the left side of the nickel trap. (See attached).
This is what I don't understand. Why didn't Western do what Northern did? Why completely redesign the part?

Stan S.

Offline Stan S

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Re: Redesigned prepay 3-slot electromagnet
« Reply #4 on: January 28, 2017, 10:14:40 AM »
Let's try the first attachment again.
Stan S.

Offline RotarDad

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Re: Redesigned prepay 3-slot electromagnet
« Reply #5 on: January 28, 2017, 12:25:43 PM »
Stan - Great info!  Thanks for the detailed explanation.  It does make sense that issues arose over time that needed later mods.  How about that "Automatic Nickel Local Overtime Feature"?  Sounds like the phone co. wanted to keep callers from tying up the payphone too long, so they started requiring an extra 5.  How did this feature work?
Paul