Classic Rotary Phones Forum

Telephone Identification, Repair & Restoration => Telephone Troubleshooting and Repair => Topic started by: dsk on April 20, 2014, 03:27:04 AM

Title: Dial tuning, is it good enough or not?
Post by: dsk on April 20, 2014, 03:27:04 AM
Hi
I had to fix a non working W.E. 5H dial, and by using eye and ear, I got a result pretty well working.
The spec are probably not OK but its working, and by PC monitoring in Audacity I got this result.
What do you think?

dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on April 20, 2014, 10:50:55 AM
Now it is tuned. (its fun to play with this)
The speed varies a little around 10 pulses pr sec. That's better than to have higher tension on the spring.
The break ratio are no approx 65 %  (UK standard are set to 2/3 or 66.7% and US and Norway uses 60%)
The exchanges use to accept both standards so this seems reasonable to me. (my own standard  ;) )

dsk
 
Title: Re: Dial tuning, is it good enough or not?
Post by: Mr. Bones on April 20, 2014, 02:28:34 PM
Dag,

The vast majority of members here know infinitely more than I do about dials. That being said, 10.07 p.p.s. certainly ought to be more than close enough. Looks like you got the make / break ratio down pretty good, as well.

I've had Audacity for years; will have to figure out how to utilize it in this fashion.

Best regards!
Title: Re: Dial tuning, is it good enough or not?
Post by: Scotophor on April 21, 2014, 02:03:26 PM
It looks reasonably good to me. Info I have from various sources gives slightly different details regarding U.S. dial specs. The one I consider most authoritative has the following:
Pulse rate = 10 pulses per second nominal
phones being refurbished should be adjusted to within 9.5 to 10.5 p.p.s.
phones in use are considered OK within 9.0 to 11.0 p.p.s.

Break-to-make ratio = 62% break nominal
phones being refurbished should be adjusted to within 62 2% (60% - 64%)
phones in use are considered OK at 61.5 4% (57.5% - 65.5%).

If your phone dials out reliably it may be just fine on your system (especially if it is meant to handle both U.S. and U.K. dials), but according to this, 65% break is very close to the limit for U.S. dials.
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on April 22, 2014, 06:11:10 AM
I've been asked to share how I do this.
Assuming you know Audacity (free) you plug in a suitable cord. to the microphone jack.
(I have used one with male plug in both ends. )
Connected tip and sleeve to the pulse-contacts (or line cord) with some test cables with clips.
To get a better reading adding a sound may help, I just connected my signal generator (picked from a container) to the same 2 points.
I guess if you use a radio with some hissing sound, you should protect the radio by using a resistor in series with the output from the radio.  You have toe experiment withthe record level, I used some 30%.   Start recording, dial zero, stop recording.
Zooming in to start and end of the first and last break and makes between pulse 1-2 and 9-10 will give you pretty good timing data.

dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on April 22, 2014, 07:13:23 AM
The last thing is the math, i have made a simple spreadsheet, using the 6 points marked in the first picture and calculates what I believe are reasonable good data, based on visual observation of a smooth and nearly constant speed on the dial return.

I have not found any way to share the spreadsheet but a pm to me with your email address and I'll mail it to you.

dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on October 04, 2014, 01:55:32 PM
Always learning!
Today my Norwegian payphone went to strike! The dial would not work. I picked it out, and measured up and down in every manner I could, its perfect! nearly 0 ohms at closed contacts, breaking properly, perfect rate 11pps.

At last after testing with other dials, no it has to be that dial, a little drop of greasy oilish gel was in the pulse contacts, so cleaning again, and yes its working. This kind of errors are extremely frustrating, and hard to find.

dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on April 07, 2015, 02:15:55 PM
Audacity is just great.
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on October 04, 2015, 12:16:43 PM
I got the question about why  measuring 9 pulses, here is my answer:
The pulse registered by the exchange is break.  The exchange still need a pause between the breaks, this has been deemed to be with a preferred length. Here we use 60% break, 40% make, UK use 2/3 to 1/3.  If the make is considerably shorter, it may not be recognized, and the 2 breaks looks like one long break, or a flash.   After the last break the circuit remains closed, so it will be hard to tell the length.  That makes it hard to measure the last make, so I measure from the first break opens, to the tenth opens. Only 9 pulses  (brake   make) should last for 9/10 of a second. (at 10 p.p.s.)
Then I calculate those 9 divided on the time consumed (displayed in audacity) and get out the dial speed pretty accurate.

dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: andre_janew on October 04, 2015, 12:25:25 PM
Of course, the real test comes when you try to dial out with the phone.  This is the most important test of all!
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on October 04, 2015, 12:40:54 PM
You are absolutely right, and many exchanges accept great inaccuracy, this are more a tool during tuning. No need for repair when it works.

dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on October 04, 2015, 04:52:51 PM
Here is an example of a slow dial:
(approx 7 pps and it should be 10.)
dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: TelePlay on October 04, 2015, 07:24:20 PM
And this is a WE #6 dial as removed from a phone showing a bit of a problem. Audacity not only helps determine PPS but is also a great tool to identify why or where the pulse problems are happening.

This excel spreadsheet I devised lets me calculate the PPS over any number of digits dialed, the break/make ratio of any digit, the individual break/make ratio of all digits and the average break/make ratio of all 10 digits dialed. Overkill, yes, but  it can be used to find minor flaws or dirt in the gear train to be corrected.

This spread sheet is for a #2 dial that is a bit slow, not the #6A dial with problems shown in this reply.
Title: Re: Dial tuning, is it good enough or not?
Post by: TelePlay on October 07, 2015, 03:30:43 PM
This is the improvement from one ultrasonic cleaning and no oil yet applied. Same WE #6A dialed in the last post but working better.
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on October 07, 2015, 04:26:46 PM
This should be good enough, a little oil may do a difference, and at least make it live longer. You should probably not do any adjustments between 9 and 12 pps.
dsk
Title: Re: Dial tuning, is it good enough or not?
Post by: TelePlay on October 07, 2015, 10:13:49 PM
This should be good enough, a little oil may do a difference, and at least make it live longer. You should probably not do any adjustments between 9 and 12 pps.

Yes, I agree. When I have more time, I want to put some sort of gentle rust remover on the spring only and let it sit for a while before doing another ultrasonic cleaning. Then, after a few days of drying, I will oil it to get the final dial speed results with a rust free dial, lubricated dial.

For some reason the spring was rusty. I have photos and will post them tomorrow. Posting this here to document the effectiveness of ultrasonic cleaning on dials. Does a nice job with the right cleaning solution. And Audacity is very good for this. Only about 0.05% of the software is used but with the ability to expand the recorded sound to 5 digits after the decimal in seconds provides more than significant accuracy in determining dial speed. I use 3 digits after the decimal point, more than enough for this analysis.
Title: Re: Dial tuning, is it good enough or not?
Post by: TelePlay on October 08, 2015, 09:03:25 PM
This should be good enough, a little oil may do a difference, and at least make it live longer. You should probably not do any adjustments between 9 and 12 pps.

Cleaned most of the rust off of the main spring, gave it a second 20 minute ultrasonic cleaning, rinsed it with distilled water, blew it dry with compressed dry air and oil all bearing points. Looks good. Will retest it again in a few days to see if seeping oil makes any changes.

This is the speed analysis of the dial as removed from the phone

(http://www.classicrotaryphones.com/forum/index.php?action=dlattach;topic=11721.0;attach=129957;image)

This is after cleaning and oiling.
Title: Re: Dial tuning, is it good enough or not?
Post by: dsk on October 09, 2015, 07:26:09 AM
This shows the effects of cleaning, and oiling in a scientific manner. Good!
 :)

dsk