atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Telephone Repairs & Equipment 2554BMP dialing problem

Hi all,

I just got a Western Electric 2554BMP: wall mounted, chrome cradle, manufacture year: 1976

It rings and answers calls perfectly. It gets a dial tone, but it has problems dialing.

All of the keys produce a tone, but only "*", "0" and "#" will "register".

Here is what happen.

- pick up the receiver, get a dial tone
- press "1" or any key up to "9": a key tone is produced, however dial tone continues (that is not normal, right?)
- press "0" or "*" or "#": key tone is produced, and dial tone stops as expected.

It would seem that only 9 of the 12 keys are actually "heard", although they all produce a tone.

This is my first exposure to old telephone technology, so I don't really know where to start.
Any help will be greatly appreciated!

Thanks,
Mike

Try reversing the tip & ring (Red & Green)wires on the incoming cable. Some earlier dial pads were polarity sensitive.

Thanks MooreTel.

I should have mentioned that I already tried that, but it had no effect. Even with the polarity reversed, only 3 of 12 keys work.

Thanks,
Mike

Try cleaning the dial contacts with a either typing or copy paper, you can use alcohol if they're real bad.

Next step would be to check the wiring on THAT phone with another 2554 or 2500 set. Of course the dial pad could be defective. Changed a few in my day.

Thanks/Merci!

I guess the next step is to take apart the dialpad and see what can be done. I'll make sure to report on my progress.

Mike.

Oh, and I will also check the wiring (je vais verifier le cablage ).

I just found the right resource from another post:
https://www.sundance-communications.com/cgi-bin/ultimatebb.cgi?/ubb/get_topic/f/32/t/000076.html

The frequencies could be off. When you hold down two keys in a row, or two keys in a column, do you hear a single tone?

Do you have another touch tone set, and 4 hands? Take them both off hook at the same time, press 1 and 2 on both sets at the same time, and listen to the resulting "beat" frequency. If it is wavering, the tuning is off. Compare with 1 and 4 as well.

The transformers have a slug in the center that can be turned to retune, BUT, it is usually a triangular slot, and a metal instrument inserted into it will change the frequency while tuning. We used to shave an orange stick to fit, so no interference with metal, and less chance of shattering the tuning slug.


.

Aha! That's very interesting.

Yes, I hear only one single tone when I press two rows or two columns keys at once.

I only have one of those old sets to work with, however I can easily reproduce the individual tones at the right frequency from my computer for comparison.

I have found the frequencies here: https://en.wikipedia.org/wiki/Telephone_keypad

I'll try that.

Thanks,
Mike

Mike, the contacts that you should be concerned with are the ones around the sides of the dial, not the ones on the back. Since each button's frequency is actually a combination of two tones, one dirty contact can distort the tone generated from several buttons. It is fairly unusual for so many of these contacts to fail at the same time, but if the phone has been stored/inactive for a long period, anything is possible.

Remember that you have a 3 x 4 matrix of tone combinations, so with only one row of buttons working, you likely have 5-6 dirty contacts. Be cautious about attempting to tune the transformers. The tones are very, very precise and when you start messing with both transformers, you may never get a perfect match again using the human ear.