Western Electric 302--- dial tone issues

Adam,

Any chance you reversed the tip and ring connections when you did the re-furbishing? The reason I ask is that the phone ringing signifies both leads are making contact, but since the ringing voltage is AC, polarity does not matter. This may not be true for the on/off hook (I'm not familiar with that old of a vintage of phone...) since it uses the -48VDC and that circuit may have an internal diode which would prevent the Telco office from sensing the current and sending the dial tone.

Good luck and post your results.

Bob

Hi Adam...

The telco detects a load on the line through the hook switch, but not a dead short :) I think you're going to find that the load is made up of both the reciever and the transmitter. Seeing you hear noise and intermittently dial tone, I'd double and triple check the transmitter. Both in the handset, if you can get to it, and of course the wiring.

The delay between the two switches opening is merely to ensure that the phone doesn't ring in your ear :)

Take care.

Ken

I've got a couple of 1950s and 1960s 500 sets. One thing I've noticed is that these sets, if the line cord is original, have three wires - red, green, and yellow. Red and green are ring and tip and yellow was originally ground. If you don't hook up the yellow, sometimes these sets don't work. If I remember right, connecting the yellow to the green wire makes it work.

I don't know if the older dials have this same problem, but you might look at

.

Is it possible that one of the internal wires has broken inside the insulation? An ohm meter will tell you pretty quickly.

You might dig around on this site:

. If the info doesn't help, I think there are links there to people that fix old phones.

If you can't think of anything else, find out where your local phone exchange is. Go there around noon when the linemen are sitting in their trucks, eating lunch. Find the oldest one and trade beer or whatever for phone repair services.

Matt Roberds

Does the resistance into the phone go low when it's off-hook?

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Just working from memory--distant memory--and referring to symptom #2 above, it sounds like the issue may be in the dial mechanism. Given that the dial makes/breaks the line connection in order to function, and further given that a dial tone can be obtained, however briefly, by moving it...it seems to me to be a contact issue within the dial itself.

I could be wrong, but....

jK

Probably two wires are swapped.

Perhaps double check the wire colors if that's what you're going by.

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They didn't have diodes in 1941 of the kind you are thinking about

H. R. Hofmann

They didn't have diodes in 1941 of the kind you are thinking about

H. R. Hofmann

Hi...

I stand ready to be corrected, but to the best of my recollection there were none at all - save mercury vapor tubes...

Had to carry the radio battery down to the corner gas station to have it recharged once in a while... until Rogers invented the rogers batteryless radio :)

Matter of fact if any history buffs are out there, that resulted in a radio station in Toronto - CFRB, where the RB is Rogers Batteryless.

And today that station still continues, as well as all of the offshoot Rogers stuff; like Rogers Cable, and Rogers cell network, etc.

Ken

What year did selenium rectifiers come into use?

Though I can't remember the name, I thought there was also some other non-tube diode that was in use.

There's little reason to expect either in a phone from that vintage, but that doesn't mean there weren't such things.

Michael

Hi Michael...

Got my old memories going again... googled everywhere I could think of and can't find any reference to any rectifer pre-dating selenium.

Gee, speaking of memories... anyone else remember the odor of one of those selenium plate rectifiers when the load was shorted? :)

Yikes.

Your telephone... dunno if my message on the subject got lost in cyberspace, but still think you should check the transmitter and wiring.

An experiment? Plug it into a jack that's part of your house system Leave it on hook; get someone else to pick up another phone and make a call to a friend. As soon as they're connected and talking, you pick up your handset - see if you can hear and talk to them.

Take care.

Ken

}Hi all! } }This might be a long shot... but here goes. } }I have an old, 1941 Western Electric Model 302 Telephone. This is a }'real' phone, and has always continued to work flawlessly... until.... } }We took the phone apart to clean and polish the case,

(snip-pity doo-dah)

Please measure ohms across wires to CO 1) on-hook and 2) off-hook and report back.

Stan.

Suggest you measure current flow instead using a small resistor as there will be nominal -48VDC (-52VDC @ high battery) across the tip and ring terminals which will blow out most ohm meters.

Bob

"Michael Black" bravely wrote to "All" (12 Oct 05 03:15:47) --- on the heady topic of "Re: Western Electric 302--- dial tone issues"

MB> From: snipped-for-privacy@FreeNet.Carleton.CA (Michael Black) MB> Xref: core-easynews sci.electronics.repair:344872

MB> Ken Weitzel ( snipped-for-privacy@shaw.ca) writes: > snipped-for-privacy@att.net wrote: >> They didn't have diodes in 1941 of the kind you are thinking about >>

MB> What year did selenium rectifiers come into use?

MB> Though I can't remember the name, I thought there was also some MB> other non-tube diode that was in use.

MB> There's little reason to expect either in a phone from that vintage, MB> but that doesn't mean there weren't such things.

Michael,

I think there were all kinds of metal/metal-oxide rectifiers in those early times. They weren't very good but that's all they had. Selenium was just a more evolved type.

A*s*i*m*o*v

... Thomas Edison invented the "Light Emitting Resistor"

Try googling for Copper Oxide rectifier. It was used in a A battery eliminator my Dad had in the 1930's

Then there were aluminum "wet" rectifiers used to get the high voltage DC for some Ham transmitters.

Bill K7NOM

Yes, it was metal-oxide rectifiers that I was thinking of but couldn't remember the name.

Michael

Adam-

The responses to your question appear to contain all the information you need to find the source of your problem, but scattered among them!

Basically, the phone presents a relatively low resistance across the phone line when the hook-switch closes. Reacting to the resulting current, a current-sensing relay at the central office closes, and a dial tone is sent back down the line.

The telephone's dial is also connected across the phone line. When you dial, a short circuit is intermittently connected across the line to generate a number of higher-current pulses corresponding to the number dialed. In your case, the current caused by dialing activates the current-sensing relay, which had NOT been previously activated by the hook switch.

Using an Ohmmeter in conjunction with the diagram, you should be able to troubleshoot the problem. As someone mentioned, you must disconnect the phone first, because the 48 Volts DC from the phone company might damage your meter!

Someone mentioned a third wire that had to be connected to get a phone to work. Modern telephones use two wires to connect to the phone company, but early phones had a third wire used for party lines. In addition to using different ringing frequencies to signal individual parties on the line, the phone company also could apply the ringing voltage from one side of the line to ground, the other side of the line to ground, as well as line-to-line as is done today. If such a third wire were not connected, the ringer would not work but calls could be made.

Fred

Lastly, the ground is the + side of the 48VDC. I share this here since the bias on the phone lines was -48VDC (below earth ground) to help prevent corrosion of the copper wires.

Another thing I seem to recall is that the scan "off hook" current requires approximately 20mA.

Bob

Good discussion, but one small correction: When you dial, the dial contacts open the current path and then close the path for each pulse. During the time that set of contacts is open, another set is closed, shorting out the earpiece so there is no click in the ear. The CO reads each pulsed open-interval. When the string of (one to ten) open pulses completes, the current path is simply maintained by the closed dial contacts.

Several people have asked the OP to measure the DC resistance of the phone while it is off-hook and NOT connected to the line. I don't believe he has responded.