Author Topic: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?  (Read 575 times)

Offline JimG2100

  • *
  • Posts: 6
Glad to have found this forum, and I've been assured by the admin that it's not a fatal breach of etiquette to ask for help with a touch-tone model.

Would appreciate some explicit direction. Never worked with a phone internally before and certainly never replaced a broken (six-wire) internal jack.

My father had brought this home after it was discarded at work back in the late 20th century. Believe it originally was some sort of multiple line, and/or multiple location ringing and pickup business telephone.

Would like to wire it for normal 2-wire single-line home landline use (modular).

Unfortunately I wasn't able to usefully understand the schematic I found linked at the bottom of this page.

Tried to visually trace red and green from the phone's broken 6 wire jack (best guess is marked in photo). But have a feeling it may have to involve more wires than those two to enable normal ring and voice and touch-tone functioning.

Not sure a home-style two conductor cord connector plug will fit into it properly, but poking around online found a couple of possible replacement jacks #623D or #616D that look as if they might fit the phone. Then, if I can find out internally where to connect the spade-tips …

Thanks for any advice.

-Jim

Offline poplar1

  • Hero Member
  • *****
  • Posts: 5876
  • 102C-6 = "Old Brass" Hand Telephone Set
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #1 on: July 31, 2017, 05:22:19 AM »
You need a 623D. Doesn't matter if the 623D has 2, 3, 4, or 6 wires because you need to connect only 2 --  red and green.

616D is only for the handset cord.
"C'est pas une restauration, c'est une rénovation."--François Martin.

Online Ktownphoneco

  • Hero Member
  • *****
  • Posts: 687
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #2 on: July 31, 2017, 09:40:30 AM »
Jim   ...    Welcome to CRPF.    There is a lot of help available here, and some "VERY" knowledgeable people who can answer any question regarding telephones, but I'm not one of them.

However, in relation to your 2500-MM set :   If it would be helpful to you, I can scan the schematic (wiring diagram) for your 2500-MM to illustrate what your dealing with now, and I can scan the schematic of the model / type 2500-D, which is a simple Western 2500 wired for single line residential or commercial service, the one your trying to achieve.   
By way of a quick comparison between the 2 schematics, you'll need to make some wiring changes inside the set itself.

If you want the scans, let me know and I'll do that this morning and post them for you.

Enjoy the day.

Jeff Lamb
« Last Edit: July 31, 2017, 11:05:47 AM by TelePlay »

Offline poplar1

  • Hero Member
  • *****
  • Posts: 5876
  • 102C-6 = "Old Brass" Hand Telephone Set
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #3 on: July 31, 2017, 09:45:42 AM »
Connect green wire from the 623D to F and red to A. If you can't dial out, reverse the red and green.

No need to try to wire it like a 2500D or 2500DM. Those models have a different ringer and a different line switch.
« Last Edit: July 31, 2017, 09:49:52 AM by poplar1 »
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline JimG2100

  • *
  • Posts: 6
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #4 on: July 31, 2017, 04:22:05 PM »
Thanks so much for the responses.

Quote
> You need a 623D.
623D it is.

Quote
> I can scan the schematic (wiring diagram) for your 2500-MM
Appreciate the kind offer, but no need to scan, here's links to the schematics from another website 2500MM 2500D.  It's just I couldn't read them in a useful way.

Quote
> Connect green wire from the 623D to F and red to A. If you can't dial out, reverse the red and green.
I was unnecessarily concerned about more than R and G wiring since a post I came across on some other business phone called for connecting a third wire to one of the two to get it working.
I do see F and A in the NETWORK section on the schematic, but not physically marked on the wiring block.

So...

For the heck of it, decided to try the terminals I had guessed-at/marked in the second photo.

Stripped a modular cord at one end and alligator-clip jumpered red and green to those terminals. Dial-tone and ring OK, but not touch tone dialing. Switched the wires and everything seems to work, even automated phone-menus can "hear" the tones.

Would these be the correct terminals to use when I get the 623D jack, or are there better and safer ones?
« Last Edit: July 31, 2017, 04:31:33 PM by TelePlay »

Victor Laszlo

  • Guest
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #5 on: July 31, 2017, 07:26:22 PM »
When you get a line-cord jack, it might have two, three, four, or six contacts. The middle two (looking into the jack) are the ones you want to use. The colors are usually red and green.  There are no alternatives, safe or otherwise.  There are correct ones, and incorrect ones.  Use the ones that are called out in the BSP for T & R.

Your phone is actually a single-line (SLT) set that is intended for use in a business environment, where there is a 1A2 system. The general code for a DTMF SLT is 2500. The next arbitrarily-chosen character is an "M" which indicates that the phone has the facility to close the yellow and black line cord leads when the phone goes off-hook. The next character is the "M" that indicates that the set uses Modular cords.  If the next (3rd) alpha character were a "G" the set would be equipped with a polarity Guard, which would allow the dial to work regardless of the polarity of the 48 Vdc applied to the cord.

The phones came with a warning sheet that stated that they should not be used in a residential installation, because the assumption was that houses and apartments MIGHT have previously been wired for 8 Vac on the second pair (yellow/black) in the inside wiring, for dial lamps in 500P/U, Princess® or Trimline® telephones.  Taking a phone that is equipped with the "A-lead" contact closure off-hook would place a direct short across the left-in lamp transformer, which would be a fire hazard.

Another issue might be that the home has two lines, and the second line is wired on the second pair of the inside wiring. Your phone going off-hook would short out the second dial tone, whenever you made or received a call.  Not good for household harmony.

The 5th and 6th leads, generally white and blue, were originally designed to energize the ringer in the set in certain installations. 

If you install a jack with more than 2 conductors, just insulate and store the extra spade lugs inside the set.  The best way to ensure no electrical problems is to use a 2-conductor line cord. You can recognize them by carefully inspecting the plugs and observing the two, rather than 3, 4 or 6, gold contacts inside the plug.
« Last Edit: July 31, 2017, 09:54:33 PM by Victor Laszlo »

Offline JimG2100

  • *
  • Posts: 6
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #6 on: August 01, 2017, 03:53:31 AM »
When you get a line-cord jack ... The colors are usually red and green.  There are no alternatives, safe or otherwise.
Thank you for the warnings. And yes, absolutely plan to use Red and Green (Tip and Ring) only, in this single line 2-wire home environment.

My last question, rather, was about where best to attach those red and green wires internally. There are quite a few positions on that terminal block in the phone, and the ones I test-connected (photo 2, original post) were selected by trying to visually follow red and green from the pins of the currently broken jack.

That test connection worked, but as a nearly clueless newbie I'm hoping for confirmation that these would indeed be the "F" and "A" connection points recommended by poplar1, or be pointed to the preferred "F" and "A".

PS That was very interesting detail on this phone and its possible wiring pitfalls outside of the intended environment.
« Last Edit: August 01, 2017, 03:59:08 AM by JimG2100 »

Offline poplar1

  • Hero Member
  • *****
  • Posts: 5876
  • 102C-6 = "Old Brass" Hand Telephone Set
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #7 on: August 01, 2017, 11:37:08 PM »

My last question, rather, was about where best to attach those red and green wires internally. There are quite a few positions on that terminal block in the phone, and the ones I test-connected (photo 2, original post) were selected by trying to visually follow red and green from the pins of the currently broken jack.

That test connection worked, but as a nearly clueless newbie I'm hoping for confirmation that these would indeed be the "F" and "A" connection points recommended by poplar1, or be pointed to the preferred "F" and "A".


The terminals that you indicated are indeed F and A. The letters are difficult to see because they are the same color (white) as the block.
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline JimG2100

  • *
  • Posts: 6
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #8 on: August 02, 2017, 01:18:22 AM »
Thanks very much to all for the explicit help, and the stimulating information, on this 2500MM.

I look forward to using a telephone that's not merely a PCB in a puff of plastic!

Offline petergmauro

  • *
  • Posts: 1
Re: Help in adapting 6-wire Western Electric 2500MM to 2-wire home use?
« Reply #9 on: February 27, 2018, 07:32:17 AM »
Hi folks,
I have a AT&T 2500MMGJ , that is not connecting the dial tones to tip and ring.
I'm not sure what the " J " means.
I can hear the dial tones in the earpiece , so I know it's working , the complete hand set works fine , it just doesn't
impress the dial tone to the line connections.
The internal circuitry is completely contained on a printed circuit board, with none of the standard markings ,
such as  "A"  , "F  "  L!, L2 etc.
Can anyone help ?

Peter