Need help restoring and wiring a WECo 151-AL / 634A Subset

[unbeldi]

Here are diagrams of the 151AL/634A combination from my circuit studies (first circuit), and the 302 telephone for comparison.

Both circuits are identical with respect to their electrical functioning during a call when off-hook.  The only difference is the placement of the switches.

Using circuit diagrams drawn in the exact same manner, makes the comparison easier.   The different placements of the switches makes all the difference in the world, when it comes to diagnosing failures,  and those are especially difficult to follow in most wiring diagram presented in BSPs or elsewhere.

Indeed small differences in timing can be crucial in eliminating or confirming certain causes.

Once again, I can only recommend taking the little time it takes to read a circuit diagram and learn to draw one yourself.  Most telephone circuits are so simple that anyone can learn them.  They have the smallest amount of electrical components than any other circuit I can think of.

In these diagrams,  a cross over a line  —X— stands for a normally open switch  while a simple bar across a line, —|—, is a normally closed switch.  This is a convention used predominantly by the switching community, because it simplifies the diagrams tremendously, eliminating all the details of other switch symbols. The switchers have very complex switching arrangements to deal with.

When the line is broken with two bars, e.g.  ——| |——, with a clear space in the middle, it means this is a condenser (capacitor), which in fact litterally are two metal surfaces facing each other in parallel. The space nicely illustrates that no steady direct current can flow through a capacitor.  The old symbols in telephone wiring diagrams are much more elaborate and clumsy.

The presented state of each is in the normal on-hook condition.

[poplar1]

I have tested each of these segments within the transmitter circuit and narrowed it down to no conductance in the black conductor in the wiring harness.  Would a broken black conductor have the characteristics that I described?

Tina

Yes, that's exactly what I suspected all along: an open transmitter circuit. If the black harness wire is open or missing, then that is the same as not having a transmitter connected at all.

You could install a temporary replacement wire from BK on dial to the transmitter.

[cloyd]

Unbeldi,
You are right, I should learn how to read the diagrams.  Actually, I already have it on my to do list.

Poplar1,
Now that I have time to tinker some more, I will try replacing the black conductor.  Fingers crossed!

Thank you both for your help!

Tina

[cloyd]

Hurray!

That did it!  Replaced the black conductor and it works great!

Thank you all!  I am very happy. 

Tina

[poplar1]

Here are diagrams of the 151AL/634A combination from my circuit studies (first circuit), and the 302 telephone for comparison.

Both circuits are identical with respect to their electrical functioning during a call when off-hook.  The only difference is the placement of the switches.

What about when the dial is off-normal? Since there are no dial terminals in your diagram, I'm not sure I'm looking at them correctly. However, both diagrams seem to short L1 and L2 (or L2 and R of IND) when the dial is wound up. However, there is no R terminal on a 2A dial (or it is strapped to BB on a 4H/5H/6A dial).

If indeed they are both creating the same short, then one should hear the burst of dial tone, with the transmitter open, after releasing the dial.

[unbeldi]

What about when the dial is off-normal? Since there are no dial terminals in your diagram, I'm not sure I'm looking at them correctly. However, both diagrams seem to short L1 and L2 (or L2 and R of IND) when the dial is wound up. However, there is no R terminal on a 2A dial (or it is strapped to BB on a 4H/5H/6A dial).

If indeed they are both creating the same short, then one should hear the burst of dial tone, with the transmitter open, after releasing the dial.

The off-normal short is placed differently, the 302 set shorts the entire phone, including induction coil, while the 151AL/634A keeps the induction coil primary in the signaling path.

For the purpose of understanding the switching principle, I don't think the terminal names are really important, they can be looked up elsewhere, although it might be good for purposes here in the forum.  At least the switches are marked as ON (off-normal), DP (dial pulse), and HS (hook switch).   What I should have indicated though is which switch closes or breaks last or first. I usually do that, but when I drew these that aspect was not my focus. It is kind of easy to figure out which one should close or open first anyways, to protect one's ears.

[cloyd]

The dial is a 4H with a strap between R and BB.
I am getting no dial tone burst when releasing the dial.
I have tested the phone by dialing calls, receiving calls (through the Panasonic 616) and by dialing out and calling my cell phone.  All seems to work correctly.  The volume could be louder.

Tina Loyd

[poplar1]

The burst of dial tone was just for testing the secondary (receiver) circuit with the transmitter disconnected, so don't worry about that now.

[poplar1]

The volume could be louder.

Are you using a 706A receiver or a 144? If it is a 706A, it takes the same HA1 receiver unit as found in an F1 handset. Do you have a 302 you can borrow a receiver from to see if the problem is with a weak receiver unit in your 151-AL?

[cloyd]

This is my receiver.  I think it must be the 144.  I was thinking that the diaphragm might be too far gone.
I am anxious to hear what you think.
Tina

[unbeldi]

This is my receiver.  I think it must be the 144.  I was thinking that the diaphragm might be too far gone.
I am anxious to hear what you think.
Tina

Yes, that's a 144.
They are certainly not nearly as efficient as the 706/HA1 type, and  can sound a bit hollow.

Make sure that the diaphragm is perfectly flat, when removed from the receiver.  It should have no warp.  And it should be pulled to the receiver magnets with certain pull.  Don't tighten the cap over it with force, just enough to secure it.

What is all that red tape on the receiver core?

The green wire is connected correctly to the terminal by which the 75Z designation is punched.

[cloyd]

Thanks unbeldi,

If the 144 is inefficient, does that mean that, historically, it has never had much volume?

After sliding the diaphragm off the magnetic receiver, it looks flat.  The magnetic pull is strong and when it is on the receiver, the center dips ever so slightly. The volume doesn't change when I loosen or tighten the cap.

The red tape came with the phone.

The white wire looks properly seated but I haven't cleaned the contacts at all.

Tina

[unbeldi]

Thanks unbeldi,

If the 144 is inefficient, does that mean that, historically, it has never had much volume?

Well, I don't know how bad it is for you.

'Volume' is relative, for example:  I use a milliwatt tone generator to compare receivers. The generator produces a constant tone of 1000 Hz at a constant power of 1 mW, that's why it is called a milliwatt (mW) tone.   Comparing a 144 receiver on a No. 51 candlestick, with a 302 telephone side by side, I find that the 144 is actually louder.

Now, the candlestick is a sidetone instrument, and the 302 is an anti-sidetone set, so the comparison is not quite fair.  An anti-sidetone circuit, despite being more modern in historical perspective, is actually slightly less efficient than a sidetone circuit.  I don't have a 151 with a 144 receiver handy right now for testing, but have the 51 on my desk.

However, when comparing general conversational speech, the 302 sounds louder, perhaps 'fuller' in sound is a better term.   We know that the 144 receiver had sharp peaks in performance at certain frequencies, especially around 1000 hertz, IIRC, while at others frequencies the response was much lower. This distorts the sound 'impression' to the human ear.

After sliding the diaphragm off the magnetic receiver, it looks flat.  The magnetic pull is strong and when it is on the receiver, the center dips ever so slightly. The volume doesn't change when I loosen or tighten the cap.

That's good!
The ever so slight bend was by design, and is necessary for this type of receiver to produce proper results. 

The red tape came with the phone.

The white wire looks properly seated but I haven't cleaned the contacts at all.

Tina

Contacts look ok from here.

[trainman]

Should have decent volume. It could be the receiver magnet getting weak with age. Also, if these were used on a common battery line, the polarity of the receiver had to be right, or they could demagnetise with use. Could be the case from its previous uses.

[trainman]

Somewhere there is a blurb is some bsp about how to correctly pole a 144 receiver when used on a common battery line.