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western electric 302 repair

Started by thomas13202, November 12, 2018, 12:50:22 AM

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thomas13202

i have been out of antique electronics repair for several years and am just starting to get back into it. therefor i am kind of limited to my test equipment. i do have a nice vtvm and condenser tester. that is the only test equipment i have that would be useful for telephone repair.

i have a western electric 302 telephone i just bought on ebay to replace a broken modern phone i was using. the problem im having is traced to the transmitter im pretty sure. originally the phone appeared to be dead. ohm meter checks found an open handset cord. i changed the cords and now i have dial tone the phone can dial out the phone rings and i can answer a call. the problem is the other person cant hear me. the coils in the network check fine with an ohm meter. i took the transmitter out and rapped the side of it on a table while turning it but this doesnt help. i tried to bend the contacts up slightly and it doesnt help. the wiring is correct according to the schematic i found online. the hook switch works fine. the dial works fine. while i do have a sprague to3 condenser tester i dont have the clip leads for it to test the condenser. since the condenser is in series with the coil in the talk circuit if it was open that could cause my problem. i am leaning toward a bad transmitter element though.

now for my question how can one test the transmitter? i have no other phone to try it in or other transmitter to try. sorry for the newbie question but without another f1 transmitter to try or another phone to try that one in im stuck as to how to test it. i dont have a but set to connect to substitute for the transmitter either. would an ohm meter test from the center button contact to the outside contact with the transmitter element out of the phone be of any use? one piece of news the contacts are clean as can be nice and shiny so i dont think it is bad contacts.

this is really testing old memories of troubleshooting my first 302. that one had a bad hook switch. even when you hung up the phone it would stay off hook which  adjusting the hook switch contacts fixed and an open in the section of the condenser for the ring circuit and it never rang again. i had no schematic and the value of the condenser was not marked on the can. this was long before the internet so no schematics and no parts sources on line. i bought that phone from new england telephone when ma bell was broke up and you had the choice to buy your existing phone or turn it in and buy a new one from someone else. new england telephone is long gone now. even in the late 80s or early 90s when i called them about a replacement condenser they said they no longer had parts for phones. that phone is long gone now also.

dsk

Welcome to the forum. 


A transmitter capsule in series with a battery (3V) and a receiver will do.

The 302 will not work without the transmitter element, so the first easy test is to remove the transmitter and plug in the phone;
then you short the 2 springs for tee transmitter, and should get the dial tone. remove the short, and you loose connection.
If that works, start testing on the transmitter.


dsk

thomas13202

thank you for the info. ok i removed the transmitter capsule. with no short on the transmitter contacts i still have dial tone and when dialing my phone number i get my verizon voice mail so it is dialing out. it is a verizon pstn service. am i correct in assuming having a dial tone with no transmitter in the phone  means a short somewhere is causing this? it is a brand new handset cord so it cant have a short inside between the individual wires. the wiring inside the transmitter cup is bk black wire to bk on dial. white wire on bk in transmitter cup to receiver. w white wire to w on the dial. r red wire to r on network. r red wire to receiver. hook switch goes from zero to inf when going on of hook tested at connection points on network. network coils have continuity. not sure what their actual value would be so i dont know if that is correct. the only original wire in the transmitter is to the receiver inside the handset. please advise how to proceed as i dont know how to proceed farther. my background is in vacuum tube radio tv repair. i have only worked on three phones in my life.


dsk

#3
This simplified schematics are a good start.
Since the exchange register off hook when it flows a DC current it must be something to measure out. use your ohm-meter, and look for wires touching each other or put on wrong terminals. Both capacitors are non polarized and shold be for 200V or more.  Line voltage are usually close to 48, but in some systems 24 or 60
The capacitor in series with the ringer does let the AC ringing current trough (usually 80V 20Hz)  The 2 uF capacitor lets AC sound signals pass, but blocks dc because it is needed in the carbon transmitter.  Going off hook will normaly drop line voltage to around 5 V,  More here: https://goo.gl/vngcXe


Jim Stettler

Quote from: thomas13202 on November 12, 2018, 09:54:05 AM
it is a brand new handset cord so it cant have a short inside between the individual wires.

It is a brand new cord, so it shouldn't have any shorts (but it could) . You may want to meter between conductors to be on the safe side. I would meter the wires in the handset as well (I doubt if they are bad). Over the years I have wasted a lot of time  by assuming a brand new item worked properly. A 5 minute fix can turn into 2-3 hours of troubleshooting due to assuming a new (bad)  part works right out of the box.

A continuity light or buzzer would work if you don't have a meter.  The free meter from Harbor freight works fine for telephone troubleshooting.

JMO,
Jim S.
You live, You learn,
You die, you forget it all.

poplar1

#5
You should not have dial tone with the transmitter removed (unless you short the 2 transmitter contacts in the handset). Move the white jumper wire (for the receiver contact)in the handset from BK terminal to W terminal.

Quote from: thomas13202 on November 12, 2018, 09:54:05 AM
the wiring inside the transmitter cup is bk black wire to bk on dial. white wire on bk in transmitter cup to receiver. w white wire to w on the dial. r red wire to r on network. r red wire to receiver. hook switch goes from zero to inf when going on of hook tested at connection points on network. network coils have continuity. not sure what their actual value would be so i dont know if that is correct. the only original wire in the transmitter is to the receiver inside the handset. please advise how to proceed as i dont know how to proceed farther.



Not sure what you mean by "only original wire in the transmitter is to the receiver inside the handset."
Unless you have an earlier (1936-1945) handset, there should be two jumper wires, red and white, going from the base of the handset to the receiver cavity. The red jumper goes from the R terminal  to one receiver contact, and the white jumper goes from W terminal to the other receiver contact. (There is no jumper on BK terminal inside the handset). Handset cord then connects as follows: Black from BK in handset to BK on dial; White from W in handset to W on dial; Red from R in handset to R on 101A Induction Coil.
"C'est pas une restauration, c'est une rénovation."--François Martin.

thomas13202

when i checked wiring is fine. i listed the connections for transmitter wiring above. i will disconect transmitter wiring from the phone to isolate the handset. i did check across bk and r once before with transmitter and receiver elements out and got continuity between bk and r in the transmitter cup but the handset wire was connected to the phone so i assumed they were connected somehow in the phone its self. i will repeat this with handset disconnected from phone and post results as soon as i can.

the new schematic you gave me has the coil values posted on it so i will check the coils against the values listed. what does tx and rx on the simplified schematic mean.

does anyone have a pic showing the wiring inside the  transmitter cup as this end is not shown on the schematic. only the conections to the dial and network are shown not the connections to the terminals inside the transmitter cup.         

i think i attached the schematic i was using to this post. i also used this list attached to this post to compare wiring to.

i do have a nice hickok 209a vtvm waiting repair and a working rca wv77e vtvm so im ok for a meter.


poplar1

#7
tx=transmitter
rx=receiver

Handset cord connects to terminals indicated: White to W, Red to R, Black to BK.

(photos from Ebay listing: https://www.ebay.com/itm/143004222178)
"C'est pas une restauration, c'est une rénovation."--François Martin.

thomas13202

i wrote the above before i saw popular's reply. is the bk terminal the one on the opposite side of the transmitter cup from the r terminal or the center terminal. if it is the one on the opposite side from r it has the bk wire and the white wire to the transmitter and bk stamped above it. if it is the center terminal it has the white wire on it. i will reverse the black and white wire from the handset cord and see if that fixes it. my problem is i removed the original handset wire from the terminals in the transmitter cup and it took a few days to get the new cord and i didnt remember how it was wired. while i found a picture with the dial terminals clearly marked so i knew for sure which terminal is which i was not able to find a pic of the transmitter cup terminals and they are not shown on the schematic. since the white wire to the receiver was on the terminal i thought was bk i put black wire from the handset cord there. it does look like it has a bk stamped above the terminal and a little to the right. the center terminal doesnt have a marking unless the bk is for that one and r is on the opposite side with r stamped above it. i will change the position of the black and white handset wires on the terminals in the transmitter cup now and post the results here.

when i said the only original wire in the transmitter cup is the wire to the receiver i indeed meant the red and white wire to the receiver. maybe i should have said only original wiring instead of wire.

Doug Rose

Just my two cents, I always like to verify the handset is working before all the trouble shooting. Disconnect the handset from the phone. Bring dial tone to the wires. If you hear dial tone and hear your self when you talk you have eliminated the handset, the elements and the cord. Techs used these for a poor mans buttset for years..Doug
Kidphone

poplar1

Do you have the two jumper wires from the receiver connected as in the photo?

If so, just connect the white handset cord to the same terminal as the white jumper (left side of photo). (terminal "W")


Connect the red handset cord to the same R terminal as the red jumper from the receiver.

The middle transmitter contact is BK and should NOT have a receiver jumper wire on it -- only the black handset conductor and no other wires.
"C'est pas une restauration, c'est une rénovation."--François Martin.

thomas13202

ok the pic you sent me clearly shows my error. i have the w handset wire on bk terminal and bk handset wire on the w terminal. i dont know how i was so dumb to think the bk above and to the right was for the end terminal instead of the middle terminal. poor eyesight is no excuse for my stupidity. i guess i need new glasses.


poplar1

The "W" is probably hidden by the spade tip of the white jumper.

Il n'y a rien cassé (Nothing broken).
"C'est pas une restauration, c'est une rénovation."--François Martin.

thomas13202

ok i put black wire on bk and white wire on w. i can now call out and be heard. no way to test if it still rings until i get a call but it should. i made a dumb mistake and own to it. ill know next time for sure.

thomas13202

mea culpa my fault. like i tell a friend of mine things work better when they are plugged in and wired  correctly. he has a tendency to try to bench test a radio he just repaired but forgetting to plug it back in after unplugging it to do the work after the initial bench test to see what is wrong.