WE #6A Dial Break/Make Adjustment

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The WE #6 dial uses two leaf springs and a oblong pawl to open and close the line to send dial pulses to the CO when dialing a number.

The image on the right shows the two terminals and associated leafs use to create pulses on the line. The leaf in "green" is a flat leaf and the one in "blue" as a contact point (red circle).

The Pulse Pawl, the white plastic oblong pawl, rotates after the finger wheel is released. About 40% of the pawl is "longer" causing the two pulse leaves of open and close in the desired 60/40 ratio of "break" time to "make" time.

The pawl pushes against the "yellow" wing attached to the blue leaf so that when the elongated part of the pawl is against the "yellow" part of the "blue" leaf, the leaf makes contact with the "green" leaf causing the "make" part of the pulse cycle (the red circle).

As the elongated part of the pawl passes by the "yellow" wing, the "blue" leaf moves away from the "green" leaf and the circuit opens, the "break" part of the pulse cycle.

A wing below the pulse pawl (the time of which is seen at the end of the "blue" leaf) moves into position when the finger wheel is released keeping the "green" leaf a constant distance from the center of the pulse pawl center axle.

The only critical moving parts after the finger wheel is released are the pulse pawl itself and its interaction with the "yellow" wing of the "blue" leaf.

Since the shape of the pulse pawl can not and should not be changed, the Break/Make ratio of the dial can be adjusted by carefully bending the "yellow" wing toward or away from the pulse pawl. This changes the distance of the contact point from the "green" leaf. This changes how long the contact is closed and opened.

Keep in mind that these leaves are spring steel and when bending the "yellow" wing, it is best to grab it with a needle nose pliers at the bend point (black circle) and bending it toward the pulse pawl. This should decrease the "break" time and increase the "make" time. For example, a dial with a 66/34 BM ratio would move closer to the desired 60/40 BM ratio.

CAUTION: do a small bend (a 10° to 15° bend is about enough to put enough stress into the "yellow" wing to cause it to be moved just a bit - the spring leaf will "spring back" to what will appear to be an unbent position, doesn't take much permanent movement to adjust the break/make ratio) and test the dial to see if the BM ratio has changed. If the break decreases to say 65, bend it a bit again. When it gets within the 60-62 range, the dial is in spec. If bending caused the break to decrease to 56, bend it back the other way to move the break time closer to 60.

CAUTION: You will not see the bend you are making. The spring steel will spring back to some position. That is why it is best to put a small bend into the "yellow" leaf and testing its B/M ratio to decide what "bend" adjustment to make next.

It is possible that the bend may put the "yellow" wing into a position that leaves the green and blue leaves in a constant contact situation. If so, simple bend the "yellow" wing back (in the opposite direction from the last bend) a bit until the leaves once again open and close. The test the dial for its current B/M ration and if not close to 60/40, try another bend.

CAUTION: Take care when bending the "yellow" wing so as not to change any other parts of the dial. This is a hit or miss adjustment but the Break/Make ratio of a #6 dial can be changed to bring an out of spec dial back into the 55 to 65 BSP preference.

I just adjusted one from 65/35 to 61/39 in 3 "bends" so I know it can be done.

Or, just send the dial to Steve Hilsz.

[TelePlay]

For my next random project, I opened up a box and found a somewhat distressed 1945 soft plastic 302. The original dial was replace with a 6A in 1956. The dial did not return. It looked clean so the DNR had to be due to lubrication having dried out over time.

With return help, slight pressure on the finger wheel with a finger during return, the dial had a speed of about 7.4 PPS and a Break/Make ration of 70.3/29.7, quite out of spec.

Disassembly, cleaning and proper lubrication on assembly brought the dial speed up to 10.2 PPS (without any speed adjustment). This is the typical result of simple service on a dry dial.

The Break/Make ratio as expected remained the same, 70/30, and will need adjustment using the above adjustment method.

This is the wave form of the dial showing the Break/Make ratio visually out of spec.

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After adjustment, the Break/Make ratio settled in at 61/39.

You can see the difference between the yellow vertical lines of the before and after wave form.

The dial speed stayed the same at 10.1 PPS in before and after B/M ratio adjustment.

[dsk]

I love to learn about this, and have adjusted some totally wrong dials, but by my experience, the speed is the most important, and it is surprisingly how much the exchanges and ATAs  etc accepts.  I ususally try to get the speed within 10-12 pps. Almost all dials has been accepted by my equipment.  The break rate has varied between 50 to 80%.  The most difficult was the old dial with long last pulse.  It ended with uneven breakes of 50 to 60 %  pulses at 10 pps.