Western Electric 302--- dial tone issues

Don-

I stand corrected, as Ken also noted.

From your explanation, it would seem that Adam should look for an open earphone connection as one possible cause of his symptoms.

Fred

Hi...

Went out to the shed, searched around a bit, and came up with an old rotary dial phone. :)

Not nearly as old as we're looking for (plastic, maybe the '60's?), but perhaps better than nothing. If the OP would like I'll be happy to take it apart a make up a bit of a schematic for it. Might be helpful.

Take care.

Ken

Did they really change much, after the obvious point where dials were introduced? One reason they were always reliable was that they were so simple, and there's little reason to change that until the time when electronics started being added.

Michael

Hi...

Dunno, sure are lighter though :)

Plugged this one in, rang it. What a flashback hearing a real mechanical bell again :)

Take care.

Ken

Without a circuit I can only guess...

You gave a clue in that dial tone is momentarily audible when the dial is moved. Could it be that in your refurbishment you have altered the spring tension on the dial loop interrupter contact?

Since the off-hook line loop condition relies upon current through this contact it may not be making firm contact when in its normal position. Also check that the other off-normal springs are also making firm contact when the dial is rotated from its normal at home position. Clean and re-adjust spring tension where necessary.

Ross Herbert

While this page

doesn't have a circuit of the WE302 the pictures appear to show 5 wires connecting to the dial.

Here is a circuit of a Kellogg phone of a similar era which is fairly typical of telephones used in the USA, UK and Australia

Note that the W,X, Y and Z springs are all part of the dial mechanism and while the Kellogg shows 6 wires to the dial springs this is because Kellogg routed the bell circuit through the W contact on the dial. In most cases manufacturers didn't do this so the dial connection can be made with 5 wires as shown in this APO 332AT telephone from the same era.

I suspect that the WE302 will be similar to the latter circuit.

Just wanted to thank everyone for all the suggestions!

I'm going to attempt another look at it this afternoon, I'll try to post a follow-up if I can get anything else working.

Thanks again everyone, Adam

Adam sent the following message on 10/11/2005 1:52 PM:

Yes, out of circuit resistance measurements across the line inputs in both on and off hook would be very useful. I also had suggested he verify the T and R were not wired in reverse since that too would give the very same symptoms (allow the phone to ring, but not go off hook properly). I've seen no reply to that suggestion either.

As someone else has already said, it seems he has received a good deal of advice and suggestions ...

Bob

has

I think the 500 set had some varistors to regulate the volume out of the mic. (transmitter). The intent was to make all telephones the same volume when the signal reached the Central Office.

Bill K7NOM

Many thanks for all of the advice! Now for the explanation of what went wrong, how I found it.... and hopefully you guys won't take away my engineering degree!

Using a wiring diagram from the web and my ohmmeter, I again reassured myself that it was wired properly. The two switches in the hook switch and three in the pulse generator all made and broke contact cleanly (also verified with my meter).

Then what to do?! Having a small stockpile of 500 series phones available, I pulled a handset off and connected it. This turns out was from a newer generation 502... but we got a dial tone! It was much much too quiet though-- which I surmise was from the speaker impedance not matching the transformer. Finding an older 502 & connecting the handset, IT WORKED!

Meanwhile as background, we had carefully cleaned the contacts on the mic and speaker cartridges for the 302. I had checked the resistance of the cartridges out-of-circuit so I knew they weren't blown. And I had checked the wires on the phone end IN-circuit. Bad Idea. Seems I was seeing the resistance across the transformer not the resitance across the mic. The simple answer--- if you disconnect the microphone cartridge, you get the same symptoms and all that was wrong was the cartridge wasn't making clean contact with the spring contacts. Cleaning them up and bending them out a little, it worked fine.

Thanks so much for all the suggestions, they did help us narrow down the search and locate the problem.

Slightly embarrased, Adam (who's usually fixing other's problems by telling them they needed to plug it in-- seems I should take my own advice!)

Thanks for sharing what you found. Glad you got it working. It should last another 65 years now since it is a genuine WE Bell System phone.

Bob

Story deleted

Thanks Bob!

And now with the advent of google archives, someone 65 years from now will go to figure out why they can only get a momentary dial tone, and find this thread and polish their silver!

Adam

Bob Shuman sent the following message on 10/16/2005 7:43 PM: