P1A ringer not working with a 4228A network

[TelePlay]

The yellow WE 921 Accent phone that I color restored had a problematic ringer, it didn't work in the phone.

I bought a replacement ringer and it didn't work either. They both tested the same way as follows:

1 ) Pulled the ringer out of the phone and hooked both up, one at a time, to a ring generator, they did not work.

2 ) Put a 0.47 uF cap in the circuit with the ringers out of the phone and they both worked.

3 ) Put the 0.47 uF cap across A and K on the network and clipped the ringers into the phone, neither of them worked.

Stumped me until I had a thought while trying to get to sleep last night so checked it out today. That "test" is after this image.



4 ) Took the 3 wires off the A terminal and clipped them together (1) with a yellow clip wire

5 ) Put a new 0.47 uF cap on the yellow clip lead (other end) and attached a green clip wire to the other side of the cap (2)

6 ) Attached the other end of the green clip wire to K (3)

7 ) Clipped one ringer wire to K (3) and the other ringer wire to L1 (4)

8 ) Attached the red and green line cord (5) to my Greenlee ring generator

9 ) With all the wires off of A, check the capacitance between A and K and it read 0.412 uF (a bit low)

10 ) Checked the capacitance at the 3 wires flipped together (yellow clip) and K and got 0.465 uF

11 ) Held the hook switch in on hook position and pressed the ring generator button - the ringer worked.

Ah, the A-K cap in the network is too small at 0.412 uF and putting an external cap on A-K would increase the capacitance between A and K to 0.877 uF, way too high. And, of course, to put the external cap in series would reduce the capacitance to about 0.227 uF, too low.

So, it seems the design of the P1A ringer makes it very sensitive to cap value with 0.412 uF too low, 0.47 uF about just right and 0.881 uF to high for the ringers to work.


The fix:

Since the 4228A network cap seems to be failing (dropping in value since 1975), putting a 0.047 uF external cap in parallel (across A and K) would increase the capacitance to about 0.46 uF, a good value for now but if the internal cap continues to fail, that value will drop over time and the ringer will stop working at point in the future. Not a good fix.

The only solution for the long term will be to put one side of the new 0.47 uF cap and 3 wires on A and then connect the other side of the external cap to the red ringer wire protected by shrink wrap.

The K terminal would not be used.

Won't look clean but it will get the ringer to work and the new cap should last forever (and not seen inside the phone).

It really helps to have a DVM that reads capacitance when troubleshooting phones. Without it, I would not have been able to figure out what was wrong with the phone. Clip leads are also necessary.

[jsowers]

Very good deductive work, John! As time goes on, we're going to have cap problems more and more with older phones. Everything has a lifespan and those of us who have also worked on radios and TVs know caps are the #1 failure component in those items. We're lucky the phones were made with such good components that many of them haven't failed. But time marches on. And as with TVs and radios, bridging a new cap over an old one is bad news because the failing cap can eventually short circuit. So your method of doing it without bridging the old cap is the best method. Thanks for posting your findings.

[poplar1]

Instead of.shrink wrap, you can also repurpose either the G or.L2 terminals, which are blind terminals for the yellow and black wires from the 623P4 line jack.

I don't understand why neither ringer will work on the tester without a capacitor in series.

[TelePlay]

I don't understand why neither ringer will work on the tester without a capacitor in series.

I don't either. I took the gong off of the first, original, ringer and without the capacitor in place, if I held the clapper in toward the center of the ringer, it would work. Holding it in a bit moved the armature a bit closer to the electromagnet, I guess making it easier to capture the armature without the capacitor in the circuit.

I would hold it in and it would ring, work. I would let go (move my finger out of the way) and it would stop ringing. Maybe someone more versed in a caps used in conjunction with a electromagnetic coil using AC voltage can explain the need for the capacitor. And the value of the cap is important in that the failing 0.412 uF cap did not work but the new 0.470 uF does. The ringer out of phone with no capacitor in series with the ringer (0.0 uF) did not work. I know, C4A and B1A and older subset ringers work for testing without a capacitor. First time I've worked on a P1M and that's what I found, discovered.

Didn't want to mess with the terminals and network, too much time invested already, so hard wired one end of the capacitor to the ringer wire. In retrospect, yes, I should have done that but I'm not going to redo it now.

With the new cap in place, it works well and the cap fits nicely between the handset mount frame and the dial. And, best of all, it works.

[rdelius]

Some telephone testers will not ring a ringer without a capacitor in series because this would indicate a fault such as a shorted capacator in a telephone.

[TelePlay]

Some telephone testers will not ring a ringer without a capacitor in series because this would indicate a fault such as a shorted capacator in a telephone.

Yes, that is not the final test. If a ringer does not ring with my Greenlee or dSine generators, I put a capacitor in the circuit. My 616 will not ring a phone unless it is complete (won't ring a ringer on the bench without a capacitor).

Just testes a C4A and a B1A. The C4A rang without a capacitor using the Greenlee, the B1A did not until a cap was put in the circuit.

With respect to the P1A, neither ringer worked with the capacitor in the network, both ringers worked with a capacitor in the circuit when not in the phone.

Nothing is ever the same when working on phones, or so it seems. Always something new or something Oh, No!

[TelePlay]

" . . .  the A-K cap in the network is too small at 0.412 uF and putting an external cap on A-K would increase the capacitance between A and K to 0.877 uF, way too high. And, of course, to put the external cap in series would reduce the capacitance to about 0.227 uF, too low.

To tidy up this problem a bit, I tried to duplicate the capacitor/ring circuit problem using new capacitors on a bread board using my spare P1A ringer.

Putting a 0.385 uF capacitor in the circuit using the same ring generator, the ringer worked. This was below the 0.412 uF value measured across A and K with all wires removed.

Conclusion is that there is more going on in the network than a reduction in capacitance across A and K to keep the ringer from working. I have no way, no desire or no time to look into the 4228A network so will never know why that network ring circuit did not work at 0.412 uF.

The good news is that the P1A ringer is not that touchy with respect to capacitance value as noted above. Bad news is I will  never know why that network ring circuit was bad, something that may be found in other networks that have a failed ring circuit.

[Pourme]

Very good deductive work, John! As time goes on, we're going to have cap problems more and more with older phones. Everything has a lifespan and those of us who have also worked on radios and TVs know caps are the #1 failure component in those items. We're lucky the phones were made with such good components that many of them haven't failed. But time marches on. And as with TVs and radios, bridging a new cap over an old one is bad news because the failing cap can eventually short circuit. So your method of doing it without bridging the old cap is the best method. Thanks for posting your findings.

I subscribe to your reasoning, Jonathan. Could explain the failure of Jon's ringer circuit. We or the next generation could be in for issues that we haven't known, yet!

[MaximRecoil]

I have some questions about this in case I ever run into the same problem with one of my phones:

1. Is the "ringing capacitor" between the network terminals A and K the only capacitor in a 425 and 4228 network? If not, what problems can the other capacitor or capacitors cause if they go bad?

2. What's the best type of 0.47 uF capacitor to use? A film capacitor like the one pictured in post #3? If so, what minimum voltage rating do you need?

3. I gather that the ringer wire which normally connects to the K terminal can be left unconnected to the network after adding a new capacitor, but what about the ringer wire that's connected to the A terminal? Does that need to remain connected to the network or can you just put a capacitor between those two ringer wires without either of them being connected to the network?

[poplar1]

1. On rotary dial phones, there is also a capacitor in the dial filter (F and RR).

3. The capacitor -- whether the internal one between A and K, or an added one -- needs to be in series with the ringer. The capacitor would never be connected in parallel with the ringer.

On some models, the line goes to A rather than L2. If this is the case, you would  have to connect the line to the new capacitor, and the red ringer wire to the other new capacitor wire. The black ringer wire goes to L1.

Note: The other P1A ringer wires (Slate, slate-red, blue) are never used except for party lines.

[MaximRecoil]

3. The capacitor -- whether the internal one between A and K, or an added one -- needs to be in series with the ringer. The capacitor would never be connected in parallel with the ringer.

Yes, I was just wondering if, after connecting the capacitor in series between the two ringer wires, if either of the ringer wires has to also be connected to its original network terminal.

I know you normally shouldn't connect both wires to their original terminals, because that would put your new capacitor in parallel with the old capacitor, which could cause issues depending on the exact problem with the old capacitor.

I think I read somewhere that the capacitor should be rated for at least 250 volts, but I don't know if that's supposed to be a DC or AC rating.

[poplar1]

250 Volts AC. The ringing voltage was 90 - 105 VAC, so 250 rating is fine.

You can use A or K (not both, unless the capacitor is open) as one place for connecting one capacitor wire and one ringer wire. Or use any other vacant terminal that does not have internal connection to any of the network components. Or remove the yellow line cord wire from G and use G terminal. L1, L2, G do not connect to network components (also S and T on a Touch-Tone network).

The capacitor is in series with the red ringer wire -- not in series with both wires. The black ringer wire still connects with the green line cord wire on L1 on modular phones.

[MaximRecoil]

The capacitor is in series with the red ringer wire -- not in series with both wires. The black ringer wire still connects with the green line cord wire on L1 on modular phones.

I thought the original ringing capacitor inside the network was connected between the A and K terminals, i.e., one capacitor leg is soldered to the underside of the A terminal and the other to the underside of the K terminal. That seems to be what's going on in the attached image.

If so, when you connect one ringer wire to the A terminal and another to the K terminal, isn't that putting the original capacitor in series with both wires?

[poplar1]

With a 4-wire ringer in a 500DM modular set, the black ringer wire goes to L1, the red ringer
wire to L2, the red-slate ringer wire to K, and the slate ringer wire to A.

P1A ringer wire is different since only the red and black are used. If you connect the red wire to A and the black ringer wire to K, then the ringer is connected in parallel with the network capacitor, but it will not ring because neither ringer wire is connected to the line, and neither is the capacitor.
              A            K.        Red Black   
L2<----->capacitor<----‐--<ringer>---------L1

[MaximRecoil]

I see. Thanks for the explanation.