Cannot hear dial tone on WE Model 500CD

[Rotorman]

Western Electric 500 C/D telephone has no dial tone
Known:  1)  Other rotary phones work perfectly on our line, or at least get a dial tone
               2)  The handset earpiece has been changed out several times to no avail
               3)  When dialed, a very faint pulsing can be heard. 
               4)  Phone uses a 425E network wired as follows:

Wires from dial:   Blue    To Ntwrk terminal    F
            Green             RR
            White            GN
            White            R

Wires from hndset:   White            GN
            Red                    R
            Black            B
            White            R

Wires from switch:   Brown            C
            Black            R
            Gray                   L2
            Yellow            L2
            White            F
            Red                   GN
            Green            L1

Wires from ringer:   Red&White striped      A
            Gray                    K
            Red                    L2
            Black            L1

Wires from line:   Red                    L2
            Green            L1

Question:  Is the wiring shown above correct, and are there voltage test points that might help in isolating just where the trouble might lie?   My suspicions lie with the switch.  I see that it might be accessed by removing the ringer / bell mechanism and then unscrewing it from the base.  I don't know if there are any serviceable parts inside or if it will just have to be replaced. Can it be sprayed with contact cleaner? 

[poplar1]

So, the phone rings, and when you pick up the handset, it stops ringing, and the person on the other end can hear you?

Try removing one of the white dial wires (from R or GN), then either the black or red hook switch wires (from R or GN). The receiver is muted by these contacts, but that should happen only when operating the dial or when hanging up. You can leave these wires disconnected while making further tests.

Otherwise, you may have a defective handset cord -- probably one of the white conductors is open.  If it is only one open white wire in the handset cord, you can install a short piece of wire inside the handset from the red transmitter terminal to one of the white receiver terminals on the back of the receiver. If you still don't hear loud dial tone, then move the one end of the short wire to the other receiver terminal. If you still don't have a good dial tone, then swap the location of the two white handset cord wires inside the phone (from R to GN and GN to R). Last test, if it still doesn't work, move the short wire to the other receiver terminal inside the handset.

[Rotorman]

Hi;  I haven't tested the ringing ability of this phone as of yet.  I consider the phone dead in the water if I can't even get a dial tone out of it, and I'm concentrating my efforts on trying to chase that problem down first.  I tested the black, red, and two white wires in the handset and get absolute continuity from handset to the network, so I think I can rule out the handset.  As for swapping the white wires from the handset, that did nothing to resolve the problem, and from what I read, there's no polarity assosiated with those two wires anyway.  Any other ideas appreciated.
    I'm very new to this and basically stabbing in the dark, and would love to learn more.  What I'd really like would be some kind of simple "ohm-out chart" that would show expected resistance or even voltage values at key junction points where faults commonly occur and under what conditions.  Is there such a chart available?       

[jsowers]

Have you checked the continuity of your mounting cord? Since you haven't tested it ringing on an incoming call or speaking to someone, then you may not even have a connection to the phone line. So please check the red and green wires of the mounting cord.

If the cord tests good, then you also need to do what Poplar1 suggested with the white dial wires in his second paragraph. The dial could easily be muting the receiver element all the time and not just when dialing.

Good luck!

[Victor Laszlo]

Poplar wrote: 

Try removing one of the white dial wires (from R or GN),

Did you do that?

Do you have the BSP in front of you?

Are you aware of the two different places in your phone where there are receiver muting contacts?

[TelePlay]

I'm very new to this and basically stabbing in the dark, and would love to learn more.  What I'd really like would be some kind of simple "ohm-out chart" that would show expected resistance or even voltage values at key junction points where faults commonly occur and under what conditions.  Is there such a chart available?     

Do you have the BSP in front of you?

Are you aware of the two different places in your phone where there are receiver muting contacts?

I doubt if Rotorman knows what a BSP is or where to find the right one and then what to look for if he had it. I read knowledge of electrical diagnostic and/or repair techniques but in what Rotorman is asking, it does not really apply to phones, does it? Yes, you can measure things but test points are really not part of phones, but I could be wrong - I've never seen that reference. This seems to be either a really simple fix or one of those like Lee58 is having with her wall phone.

As for muting contacts, you got my interest there. The dial is one place but where is the other?

There have been some assumptions made leading to possible tests or fixes but since it is not known if the phone even rings when on hook, it seems this needs a one check/test at a time process from members to diagnose the problem without causing confusion. New members like Rotorman don't know where to start and poplar1 asked a good question by way of an assumption that has not been verified. jsowers has other good first check questions. These seemingly complex to fix requests always remind me of the late 50s TV repairman who gets a call for service only to drive to a home and discover the power plug is not in the wall.

Anyway, back to the question:  Does " . . . the phone rings, and when you pick up the handset, it stops ringing, and the person on the other end can hear you?

[Victor Laszlo]

Anyone attempting to be a telephone repairman needs to own a G handset, with alligator clips on the white leads, AT A MINIMUM.  Without one, although, in a pinch, a consumer-type VOM could be of help.


With the telephone connected to a live line, the handset, as a substitute for a real repairman's test set, can be used to trace the dial tone into, and through, the phone.

Yes, you can measure things but test points are really not part of phones, but I could be wrong

You are correct that there are no "test points" where meter readings will help. Most of the phone's circuitry is "go / no go."  As I said, in a pinch, a consumer-type VOM could be of help.

I doubt if Rotorman knows what a BSP is or where to find the right one and then what to look for if he had it.

All he needs to do is answer the question. If he doesn't have the BSP yet, I can help him find it. I am sure that anyone capable of posting here can figure out how to search for and print a copy of the BSP for a 500 set, and have it handy, when I ask the next questions, one at a time, as has been recommended by the moderators, so as not to overwhelm the OP.

The OP said:

My suspicions lie with the switch.  I see that it might be accessed by removing the ringer / bell mechanism and then unscrewing it from the base.  I don't know if there are any serviceable parts inside or if it will just have to be replaced. Can it be sprayed with contact cleaner? 

The ringer does not need to be removed from the telephone for any reason. The SWHK is the last place that I would suspect a fault.  (Unless there is visible major damage or mis-adjustment of the contacts, which will be very easy to spot.)  Before the OP goes off on this wild goose chase, if he were to obtain the BSP, and let me guide him back to the proper trouble-shooting path, one wire at a time, through easy questions, he will get results quickly.

Take a look at the BSP, and find the RCVR . Then trace the two sets of leads that are screwed in parallel with the RCVR, on the network terminals. The two places that mute the RCVR unit are the f and g contacts of the SWHK and the ON contacts of the dial.

[Rotorman]

We've got a dial tone!  I disconnected one of the white wires coming from the dial mechanism, and phone finally came alive.  Out of curiosity, I removed the dial mechanism from its bracket, turned it upside down and peered at the two pairs of contacts connected to the 4 wires underneath.  One pair of contacts moves slightly when the rotor is turned, but the other pair (connected to the white wires), does not.  Perhaps I'm onto something?  Don't know if I can get to those contacts if they need servicing.  Thanks all for help from pretty much a total newbie, and for any further help on how to proceed. 

[Victor Laszlo]

Contact cleaner is seldom useful in telephony. The SWHK contacts, and the contacts on most relays and keys, are designed to be self-cleaning. They have what is know as "follow" a concept that allows contacts to wipe as the make, so that dirt does not build up on them. Without that concept, the entire System would have fallen apart quickly, if you consider that there are a gazillion contacts in a CO, and another gazillion contacts in all the phones out there.

[Victor Laszlo]

Perhaps I'm onto something?  One pair of contacts moves slightly when the rotor is turned, but the other pair (connected to the white wires), does not. Don't know if I can get to those contacts if they need servicing.  Thanks all for help from pretty much a total newbie, and for any further help on how to proceed.

Excellent!!!  Let me be the first to congratulate you! 50% of "CH" (can't hear) complaints on old 500 sets are caused by those receiver-muting contacts. You removed an unwanted short circuit in the RCVR CKT.

The contacts close (make a short circuit) when the dial is rotated clockwise, and while it is unwinding, counterclockwise.  The reason they close, and are connected across the receiver unit, is so that the user will not hear the clicks that are caused by the OTHER set of dial contacts, the PULSE contacts, which open the line to make the dial pulses. Those clicks will cause acoustic shock, which is not pleasant, and can cause permanent hearing damage.

Now, as to the actual repair: Yes, you can access them. The dial dust cover comes off, either by unscrewing a couple of little screws, on older dials, or by popping it off, in the case of more modern dials. The ON contacts can be gently adjusted with a small set of needle nose pliers, so that they are OPEN when the dial is NORMAL (not being used) and CLOSED when the dial is "ON" (off normal, or being wound up, or unwinding.)

How great does it feel, now that you are batting 1000 in the repair department?

[TelePlay]

Well, this may or may not be the right BSP. After using paul-f's site to get a BSP for a 500 C/D, I was able to find it in the TCI library at this link. Only took 15 minutes for me but I knew sort of where to look.

     http://www.telephonecollectors.info/index.php/document-repository/doc_details/2809-502-501-101-i8-ref-500-501-554-556-types-tl

For someone like me who never worked in the industry, 95% of what's printed in this document is meaningless. The wiring diagrams I can understand because I've been under the hood more more than a handful of 500s, almost all of which worked. From the point of view of mine which is I don't understand BSPs, how to read them, how to use them or which one of the many are the correct one, asking Rotorman to become a repair tech over night and help himself defeats the purpose of asking for help on the forum.

If I have the wrong BSP, please post the right one, which could have been found and posted several replies ago. It seems to me, and I might be totally wrong here, that the goal of this forum is to help members fix a problem with the minimum number of replies and does not make the new to phones member a seasoned Bell tech repairman. The thrill is getting the phone to work and using it, not becoming an expert of the phone. As I said, I may be wrong but the KISS principle (Keep it simply simple) is goal number one in getting a problem phone to work. But, then, being a pedestrian phone hobbyist, I really don't want to become or need to become an expert technician but I do rely of any one of many very knowledgeable members to help me connect wire A to slot B to make the darn thing ring. That is the fun of this hobby.

I may be way off base here but in the spirit of being helpful, I think the correct BPS is linked above and if so, it may be of help to Rotorman to see what's in a BSP, learn to read what's in them and for others to help him fix the problem of the topic.

[Dan/Panther]

Have you checked the wiring section ?
D/P 

http://www.classicrotaryphones.com/forum/index.php?topic=2767.0

[Rotorman]

it works It Works IT WORKS!!  Thanks all for very helpful tips.  Indeed, the problem was inside that plastic housing (easily removed) for the contacts under the rotary dial.  I could see the actuating lever from the gear mechanism almost touching the longer contact from the two white wires when the rotor was at rest, but not quite.  A slight bend of the tang at the end of the longer contact solved the problem, and contacts are now open (eliminating the short ckt preventing dial tone), and they close now when the rotor is turned.  I noticed the other two contacts (blue & green wired) were not moving as I turned the rotor, but then upon releasing the rotor on its return ccwise cycle, the contacts did indeed move.  Ingenious mechanism, I thought, but wondered how in hell could the one faulty contact get so badly bent to begin with?  In any case, thanks all for help in solving this perplexing problem.  BSP has somewhat confusing diagrams, at least for me.  I'm guessing there's a book out there that will explain operation in simplified logical detail, but haven't researched it yet.   
Follow-up question.  I notice someone crudely wired a bridge from the L1 terminal to the G terminal at one time.  I can't help but wonder what that is for?   

[Victor Laszlo]

L1, L2, and G (network terminals) as shown on the BSP, are blind terminals, which means they do not connect to any components inside the network.  Someone connected the G and L1 terminals to get the ringer to work, rather than just moving the Black ringer wire over to L1.

The blind terminals are used as connection points for (in this case) the two incoming wires from the Central Office, (red and green) and a third wire for a Ground connection (yellow wire in the cord.)  Tracing the incoming line on the BSP, you will see that the Ring side of the line has the red ringer wire on it. The return (black) wire for the ringer was originally intended to go back to the wall on the yellow wire, where it usually met up with the green wire. There was a time when the phone company provided a service called a "party-line" and that service required that the ringer of one of the two parties sharing the pair of wires have their ringer wire using a ground return. The practice was prevalent enough that the engineers figured that the installer could quickly fasten the yellow wire to the appropriate terminal at the wall, rather than having to take the housing off the phone to do the conversion.  Most old 500 sets that have not been molested will have the black ringer wire still attached to the G terminal. In fact, when new persons post that they cannot get their 500 to ring, the first and usually final answer is "move the black ringer wire to L1."

[TelePlay]

I notice someone crudely wired a bridge from the L1 terminal to the G terminal at one time.  I can't help but wonder what that is for?

When first put into service, the line cord had 3 conductors, red, green and yellow. The yellow was a ground wire related to the ringer.

When the phone companies stopped using 3 wires and went to 2, red and green, the network needed that bridge (or simply moving the wire over) to get the phone working again.

Nothing more than that.