Identify and fix a (perhaps) GPO 746

[TelePlay]

As for the dial speed, being just a bit fast, I would first hold the dial on its edge with the screw terminals on top. Then, with an eyedropper or pipette, fill the white governor raceway (white cup circled in red) with lacquer thinner (or an equivalent non-polar solvent that does not contain a lubricant) and operate the dial, dial 0, a few times.

Then drain the the solvent and blow the raceway dry with compressed air.

Then check the dial speed to see if it came down, if any lubricant from prior dial work, was removed and the wing brakes were better grabbing the raceway.

If some improvement but not enough, try the solvent again and re-check the dial. Repeat if necessary.

If the dial still reads fast, post the results and I can explain how to adjust the governor fly wings to slow down the dial speed.

What the above attempts to do is to clean any stray lubricant off of the inside of the raceway (white cup) and the rubber pads on the ends of the fly wings (red circles) without taking the dial apart.

[Antonio]

Hello again!
I used your excel, transformed it in sheets and I'll attach an image here; Thank you so much for this file!

First I measured twice in Audacity and got:
PPS of 10,71 and 10,77 and a Break/Make Ratio of 72,63%/27,375 and 73,12%/26,88%;

Next I cleaned the Governor with Isopropyl Alcohol (since this is the "cleanest" product I can get my hands on) and measured twice again and got:
PPS of 11,36 and 11,48 and Break/Make Ratios of 74,16%/25,84% and 73,86%/26,14%;

Next I tried to do the bending, the following 2 measures read:
PPS 11,54 and 11,48 and Break/Make Ratios of 66,27%/33,73% and 66,27%/33,73%;

After this I reconnected my phone to the router and did some test dialing. I had some misdials BUT most numbers were dialled correctly! About half the times I managed to dial good and the other half they were misdialed.

So, My next step should be:
to try and bend more the leaf?
Clean more the Governor and maybe the mechanism with Isopropyl Alcohol?
Apply some oil to the parts?

I cant thank you enough for your help!

If it would help others, or if you think it could be a good tool to have I can share the Google Sheets document I made from your Excel.

[TelePlay]

I would try "bending" the pulse leaf one more time using the angle you used to get it to drop a few percent. Bend it and test it again. Close to 60, say 61 or 62, would be better.

————————

As for the governor, I've never used a water based solvent to clean parts. I don't know what effect water has on the brake pads. Seems to have made them shinier or smoother, reduced their braking ability.

At this point, you may want to stop cleaning and try to adjust the governor itself. I did this topic some time ago on an AE governor but the fly wing design is the same as your phone.

https://www.classicrotaryphones.com/forum/index.php?topic=28413.msg271967#msg271967

Since the brake ends are inside the governor raceway, you have to bend the two fly wings in place. You want to "bend" them outward, to put more force on the brake/raceway when Dialing to slow the speed. This is done by pressing the wing against the center shaft and forcing something between the shaft and the brake pad end of the wing to "bend" the brake end  away from the shaft.

I use a round toothpick but anything like that would work. Don't try to bend the fly wing with a needle nose tool in that the resulting "bend" could easily be too much requiring bending it back, too easy to overshoot the bend using that type of tool. Again, try a little bending flex and then check the speed to see what the flex/bend did to the does and if still out of spec, flex bend it again. If you overshoot, the dial speed is too slow, flex bend out the other way.

Adjust both fly wings the same way and check the dial speed.

This is a trial and error process requiring a "bending" and testing, probably several attempts to get it right.

This is can be a tedious process requiring 4, 5 or 6 bends (or more) if you overshoot and have to adjust it the other way to get it back into spec. Getting it back into spec with one bend is possible with a bit of luck.

[TelePlay]

This image comes from the above linked topic.

The left side shows as built straight fly wings. The one on the right shows crude bends in the fly wings put there by a field service tech trying to adjust the dial speed - most likely trying to bend them inward toward the center shaft to lessen the braking affect of the pads thereby speeding up the dial. They probably used a needle nose tool and over bent the wings, over adjusting them, causing the tech to reverse the bend, and kept doing that until the dial speed was in spec.

I prefer a more gentle flexing of the metal wings which puts the fly wings in a slightly different resting position to decrease, or increase the dial speed. IIRC, first thing I did when taking that dial apart and straighten the multiple bends so that when the dial was assembled, the dial speed adjustment would start with straight wings.

It's difficult to explain the bending process but essentially

1) to slow down a dial, I hold the attachment ends of the fly wings against the center shaft and slide a round wooden toothpick between the center shaft and one of the fly wings right where it's being held thereby bending the wing outward and putting more pressure on the brake pads when dialing thereby slowing down the dial speed (do about the same thing on the other wing to keep the balanced).

2)  to speed up a dial, I would put a round wooden toothpick between the attachment end of a fly wing pushing the wing outward and then pushing the brake end of the fly wing toward the center shaft near where it's being pushed outward causing the wing to be bent inward causing the brake pads to put less pressure on the race way allowing the dial to run faster.

It's trial and error, take little steps, make little bends, check the speed and then re-bend as needed, recheck speed and repeat bending as needed.

[Antonio]

It finally works! I had another go at the pulse leafs and now it reads 59,55%   40,45% And all the numbers seem to dial correctly!

I cannot thank you enough TelePlay! Really really appreciate your help and knowledge!

I was super excited when I got it to work properly. Not only because of the phone it is but also because I was able to do it on my own (with your invaluable help of course). And I learned a few new things in the process.

Again, thank you so very much.