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Problem with WE or NE 5H dials

Started by poplar1, January 07, 2023, 01:04:33 PM

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What causes (and what can be done) a 5H dial to "catch" on return, that is, to stick, particularly when dialing a small number such as 1?

I know I can send these dials to Steve Hilsz, but I am attempting to understand why it happens.
"C'est pas une restauration, c'est une rénovation."--François Martin.


Are all of the gear teeth clean to the bottom?

Dialing 0 put a lot more tension into the main spring so the dial has a lot more momentum when returning to a stop from 0.

Dialing 1 is the least amount of energy put into the main spring which means dialing 1 would be the hardest number to keep a dial from returning to stop if the teeth are filled with hard packed crud.

Dirt filled gears is equivalent to placing the gear train assembly too close to the main spring gear on a 6/7/9 dial, jams the gears together and stops all movement.


There are two things that slow a dial down, dirt and lack of lubrication (friction). If the gear teeth aren't full of crud, the dial bearing points may be dry and need oil. In both cases, the dial mainspring has to overcome either of those, or both, issues and do so by relying on the energy put into the main spring when dialing a number.

About 4 years ago, I did a deep analysis of the mainspring energy loss as it unwound, returned from dialing 0 to a full stop. The chart below shows that data.

The graph in the lower left corner shows the dial speed slowing down from the first to the last pulse (the first pulse being "0" and the last pulse being "1" so dialing just 1 puts less energy into the dial to "get it started" unlike "0" which has max energy wound into the spring.

This dial tested was slow, 8.35 PPS (red circle), so the numbers are all above 0.1 second (10 digits at 0.1 second is 1 second to return or 10 PPS). Actual dial speed didn't matter to watch the spring's energy wane away and slow from 0.113 seconds (red arrow column) for the first pulse ("0" was dialed) to 0.132 seconds for the last pulse (as if "1" were dialed by itself).

This happens with all dials and if the dial is clean and lubricated correctly, the slight loss of energy does not matter. If the dial is dirty and/or dry, that will require more energy from the spring to complete the pulse. Dialing 1 on a dirty/dry dial may cause the dial to not return.

Then, again, it could be something else with your dial since the above is theoretical and not the result of testing or checking why your dial does not like to dial "1" well.


Thanks for this info.

It's not just one dial, but a lot of them. The resistance seems to be from the "pulse brake mechanism", specifically the "running board", to borrow an old car term. This was a quieting mechanism to overcome the loud clicks in the 4-type dials, but the flat metal piece seems to offer quite a bit of resistance to the insulated long arm of the pulse pawl (visible from the front of the dial). The most resistance (which stops the dial from unwinding) occurs when the long part of the pulse pawl is directly in line with the 2 screws for attaching the mechanism to the dial case.
"C'est pas une restauration, c'est une rénovation."--François Martin.


Wallphone started a topic long ago, 2011, suggesting that a way to make a 4H or 5H click louder was to move the brake pawl around to get the desired click.

I added updates to that topic starting here

after JimNY added a reply on 12/1/2022.

In that reply, I posted a lot of information I discovered when playing with the brake pawl, the get a louder click, made me realize that doing so caused the break/make pulses (contact open and closing) to get dirty as shown in this image

The center wave file showing the best positioning of the brake pawl.

I never studied the affect on dialing just "1" so didn't see what you are asking about.

I don't know what to do to make the dial begin to return easier when dialing "1" but it make sense that if the pawl is causing friction of sorts, dialing "0" would not show that, only dialing "1" would, a momentum thing.

There is a lot going on with the pulse brake pawl

with the rubber tip contact with the plate, the spring against the pawl arm and the positioning of the plate by way of the two screws holding it to the dial case. I've forgotten what the full movement of the brake pawl is and I don't have a 4H or 5H apart right now.

With minimal energy in the spring when dialing "1", that pawl in contact with the plate could put resistance in the system causing the dial to not want to start when "1" was dialed.

In 2011, Audacity was not know for use as a tool to record dial speed. It now only allows the dial speed to be determined but also shows the quality of the break/make contact openings/closings and from my experience with dials, the cleanest break/make pulse the better. Setting the pawl brake so that the click "sounds" louder defeats the purpose of the mechanism and results in the contacts "bouncing" creating the noisy beginning and ending of each pulse as seen in T06 and T07 above.

These are very clean break/make contact opening/closings

Might be something wrong with the rubber tip, worn or sticky or dirty causing it to not move smoothly as it impacts the brake bar. You can also adjust the brake mechanism since the brake pawl is operated by the wing of the mechanism that is moved by the large "teeth" on the pulsing "gear" (the yellow circle).

Lot of moving parts in making this adjustment to get clean pulses so it's trial and error. If you have and can use Audacity to "view" the dial's performance, that would help a lot as you make one small adjustment at a time to see what it does with the goal to get the dial to start well when dialing "1" but still have a clean pulse.


Very interesting , but if it's having more difficulty (if the '1' becomes difficult to dial), there's not much point in having a more powerful 'click' in my opinion. It may be best to adjust everything normally for the best of both worlds. But I could also be wrong since I don't know these two dial models very well.


Quote from: Contempra on January 08, 2023, 01:18:22 PMVery interesting , but if it's having more difficulty (if the '1' becomes difficult to dial), there's not much point in having a more powerful 'click' in my opinion.

That's the point here. The whole purpose of the pulse brake pawl was to make the 5H dial more quiet than the #2 and #4 dials which had a loud, and probably irritating, click to those who got the phones when they were first released. Today, people like the click but the pulse brake was to make the dial more quiet, reduce the clicking sound.

The click was almost fully removed with the #6 and later dials using a totally different type of dialing mechanism. Seems WE tried to reduce the noise of phones (for example putting a rubber dial gasket between the dial and the 302 housing and the 500 bezel "O" ring to isolate the vibrations of the dial from being amplified by the housing, especially the plastic ones).

The purpose of this topic and the other two I referenced is not to enhance the click but to make the dial sound as WE wanted it to sound, quieter than the #2 and #4 dials.


Quote from: TelePlay on January 08, 2023, 01:51:00 PM...The purpose of this topic and the other two I referenced is not to enhance the click but to make the dial sound as WE wanted it to sound, quieter than the #2 and #4 dials.

Fortunately there is, in this case, the small piece of rubber that prevents the loud click . Fortunately there is, in this case, the small piece of rubber which prevents the strong click on the photo where there is the blue circle :). Me actually, I don't mind a loud click at all or not, I like to hear a dial turn :)


The click is created by the metal on metal slapping contact in the yellow circle, not the rubber tipped brake arm hitting the brake plate in the blue circle. The rubber tipped brake arm stops the metal on metal contact that would occur after the "gear" arm cleared each pulse "tooth" in the yellow circle.

The other side of the dial has the pulse pawl that opens and closes the pulse leaf switches. A missing or improperly adjusted brake would cause a noisy electrical pulse on the line and metal wear due to the pulse arm slapping against the next pulse tooth (in the yellow circle). The pulse brake arm prevents both from happening when the dial is properly (BSP) adjusted.

A noisy electrical pulse and a loud, audible click is not desired or designed into a 5H dial, the reason for the pulse brake.

The 2011 topic saying the audible click can be made louder by maladjusting the pulse brake mechanism is flat out bad advice which causes undo dial metal wear and an electrically noisy pulse.


I took the front off of my 5H dial to look at how the dial pulse brake mechanism works. This is what I found.

These are the 7 items that need to be removed (in the order from 1 to 7) to get to see the brake mechanism in action

00 Dial 7 parts to remove to get to dialing mechanism.jpg

When the dial is at rest, the dial stop arm is against the dial stop (red circle) and the pulse brake arm is to the right. The "pulse" gear has 10 teeth numbered here from 1 to 0. When dialing a number, the pulse gear moves in the direction of the blue arrow. As it does so, the number 1 gear tooth makes contact with the brake wing causing the brake arm to move to the right and in doing so actually slightly bends the brake plate (green arrow and simulated green line bending). To dial 9 and then 0, all ten pulse gear teeth move past the brake arm wing.

01 Dial at rest.jpg

This can be seen in this image as the dial moving to the right (blue arrow) approaches 0 with the 10th pulse tooth passing by the brake wing (red circle) with the pulse brake arm to the right of the center of the brake plate (the green arrow).

02 Dialing 0.jpg

Upon releasing the finger wheel from any dialed number, the pulse gear moves counter clockwise (red arrow) and the pulse gear tooth makes contact with the brake wing (red circle) causing the rubber tipped pawl to move to the left (blue arrow) forcing it across the center of the brake plate (and causing the plate to once again bend for the pawl tip to clear) putting the brake pawl on the left side of the center of the brake plate.

In doing so, extra energy is needed from the main spring to move the pawl past the center of brake plate, slightly bending the metal plate, to get to the left side ready to do its work in creating clean electrical pulses. If the number 1 is dialed, the least amount of energy of any other dialed number is in the main spring and that low energy may cause the dial to slow as the brake pawl arm passes the center of the brake plate, the point of maximum bending, thus the appearance first asked about in this topic.

03 Dial beginning to make pulse contact.jpg

When the finger wheel is released, the pulse gear moves counter clockwise (red arrow). The first number's pulse gear tooth to make contact with the brake wing moves the brake pawl to the left bending the brake plate. After that, the remaining break/make pulses do not have to use any energy to bend the brake plate. In this image, the dial is in the break phase having just sent the pulse for the number 8 down the line and is waiting to begin the make cycle for number 7. After the make pulse for the number 8 was complete, the brake wing left the #8 gear pulse tooth allowing the pulse leaf switch on the other side to move the pulse brake arm to the right (free movement) but to be stopped by the brake plate (blue circle) in such a way that there is no vibration (or flapping/bouncing of the pulse leaf contacts causing electrical noise in the pulsing contacts) and the brake wing sits in the open (red circle) between the two gear pulse teeth waiting for contact with the next gear tooth to send the next make electrical pulse down the line.

04 Dial in break contact with pulse pawl break arresting movement.jpg

This image also shows the "break/make" ratio of the pulse gear teeth with the "make" tooth being 40% and the "break" open area to be 60% of the time in one full number pulse cycle which at 10 PPS would be 0.1 seconds.

That's how the 5H pulse brake mechanism works and it has nothing to do with the level of the click heard after releasing the finger wheel. It's all about creating/sending a clean electrical pulse to the central office and if the dial is clean, lubed and has its governor set correctly, it would do so at a rate of around 10 pulses per second, 0.1 second for each number dialed.

The brake mechanism is a complex one with many moving parts and a rubber tipped brake arm which over time may be not in the best condition. Adjusting the brake plate to compensate for wear and tear may make dialing the number 1 begin more smoothly.


The brake plate is deflected about 0.12 mm as the brake pawl moves from right to left, when the dial begins to send the first electrical pulse down the line after releasing the finger wheel.

It's a lot easier for a dial with full energy in the main spring (dialing 0) to deflect the brake plate than when the main spring has the lowest dialing energy stored in it (dialing 1).

Dialing 2 has more stored energy than 1, 3 more than 2, 4 is more than 3, etc.


Thank you very much TelPlay for the informations .


Thanks for this. Much to process now but next time I need it I know it is here.
Phat Phantom's phreaking phone phettish


Quote from: markosjal on January 11, 2023, 04:00:43 AMThanks for this. Much to process now but next time I need it I know it is here.

Do like me, put this in your favorites ;) . As far as I am concerned, the next 5H dials, I will know how to do it.