Classic Rotary Phones Forum

Telephone Identification, Repair & Restoration => Telephone Troubleshooting and Repair => Topic started by: EMpire-3 on April 23, 2011, 03:59:21 PM

Title: What to do with the ground wire
Post by: EMpire-3 on April 23, 2011, 03:59:21 PM
I have a 1954 Western Electric model 500 with 425B network and C4A ringer and I want to attach an RJ-11 modular plug to the original cord. What do I do with the yellow wire? I understand that the third conductor is no longer used in modern circuitry. So, do you just connect the red and green wires to the modular plug and clip the yellow wire off? How about inside the phone? Do you leave the yellow wire connected to the network, clip it off, or leave it "dangling" (protected with electrical tape, of course)?
Title: Re: What to do with the ground wire
Post by: Dan on April 23, 2011, 04:28:30 PM
Keep the wiring original, tape it off. Always better to keep the phone as unmolested as possible if you ever want to resell it.
Title: Re: What to do with the ground wire
Post by: Phonesrfun on April 23, 2011, 05:33:00 PM
Yes, as Dan said, tape it, or alternatively hook it to the G terminal on the network inside the phone, which is a blank terminal and not connected to anything inside the network.  If your modular line cord also has a black wire, it should be taped too. 

In instances where the modular line cord has both the black and yellow wires, some have connected both these wires to the G terminal inside the phone.  This will work 90% of the time, but still not recommended.  The yellow wire is no longer used as a ground wire, but the yellow and black wires in a modular plug are designed to be connected to a second pair.  For instance in homes that have a second line.  In that case, connecting both the yellow and black wires to the same terminal inside a phone would short out that second line.  While most houses don't have a second line, some do.  Even if you don't currently have a second line this could be a problem if you ever did add a second line or if you sell the phone to someone who has a second line.

Therefore, just to be safe, I always recommend just taping and letting both the yellow and black wires dangle.
Title: Re: What to do with the ground wire
Post by: EMpire-3 on April 24, 2011, 12:06:20 PM
Thanks guys. Thatís exactly the kind of info I was looking for. I taped off the yellow wire inside my phone and connected ring and tip to the RJ11 jack. So the modification is completely reversible. My line cord had only three conductors with spade connectors on the end, but I really appreciate the explanation of the four wire configuration.

Also, I fully appreciate the philosophy that says ďrespect the original device and donít make irreversible changes.Ē Iím a babe in the woods when it comes to vintage phones but I have a long history with old guitar amps, and nothing breaks my heart so much as a beautiful old Fender amp that someone hacked up in the 80ís in order to make it ďbetter.Ē Any device thatís still working after 50 years really canít be made any better, only different.