Classic Rotary Phones Forum

Telephone Identification, Repair & Restoration => Telephone Troubleshooting and Repair => Topic started by: Telephoner123 on February 23, 2015, 03:20:29 PM

Title: Troubleshooting PTT Ericsson 1951
Post by: Telephoner123 on February 23, 2015, 03:20:29 PM
I'm new at this and thought a good place to start would be a PTT model 1951 that I inherited from my grandfather.  It has a lot of static and the bell won't ring for incoming calls.  It doesn't have any obvious problems inside.  I tested the wires in the wall cord with a multimeter and they ranged from 6-11 ohms.  I don't know if that's OK.  The cord to the handset looked OK so I didn't bother testing those.  I also cleaned some of the contacts and hit the handset a few times to loosen the carbon (as recommended in another post).  But none of this helped.  The other posts I saw for this phone were too technical for me.

Any suggestions? 
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Matilo Telephones on February 23, 2015, 04:33:32 PM
Hi there, congratulations on your Ericsson type 1951.

It does not ring, probably because you need to make a connection/bridge between the EW terminal (yellow) and A.

Which one those are, depends on which version you have. They come in 2 different configurations, with regards to the terminals.

It should be either 9 yellow (EW) and 10 blue (A) ir 10 blue (A) and 11 yellow.

Is there diagram inside?
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: LarryInMichigan on February 23, 2015, 04:59:46 PM
My experience is that most of the transmitter capsules in those phones are noisy.  No amount of banging or tapping on them helps.  What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.  I have had to do this on many European phones because their transmitters cannot handle the amount of current which flows through them when connected to my phone line.

Larry
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: LarryInMichigan on February 23, 2015, 05:01:38 PM
BTW, most of those Dutch phones from the 1950s and 60s in North America were imported in the 1970s by Tandy and sold by Radio Shack stores.  They are quite common here.

Larry
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: unbeldi on February 23, 2015, 05:12:32 PM
Quote from: LarryInMichigan on February 23, 2015, 04:59:46 PM
My experience is that most of the transmitter capsules in those phones are noisy.  No amount of banging or tapping on them helps.  What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.  I have had to do this on many European phones because their transmitters cannot handle the amount of current which flows through them when connected to my phone line.

Larry
How large is the current on your phone line?   I am not disputing the noisiness, but I am wondering whether it really has to do with current magnitude.  You can just short your line with an ammeter set to the 100mA range or so larger to measure it.

By my observation static on European phones often comes from the cords more often than the transmitter unit, but is certainly subject to accurate or insufficient tracking of statistics.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: LarryInMichigan on February 23, 2015, 08:40:21 PM
The majority of my European phones had noisy transmitters.  Quite a few were weak.  Shunt resistors helped on some of the noisy ones.

Larry
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Telephoner123 on February 23, 2015, 09:55:01 PM
Quote from: Matilo Telephones on February 23, 2015, 04:33:32 PM
It does not ring, probably because you need to make a connection/bridge between the EW terminal (yellow) and A.

Is there diagram inside?

Yes, there is a diagram inside.  I'll take a closer look.  When you say a bridge, do you mean simply a wire going from one terminal to the other?
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Telephoner123 on February 23, 2015, 09:59:23 PM
Quote from: LarryInMichigan on February 23, 2015, 04:59:46 PM
My experience is that most of the transmitter capsules in those phones are noisy.  No amount of banging or tapping on them helps.  What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.

Is the capsule the sealed thing in the part that goes against your ear?  Would the resistor go in the handset?  or the main part of the phone?  I wasn't able to remove the capsule.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: unbeldi on February 23, 2015, 10:08:06 PM
Quote from: Telephoner123 on February 23, 2015, 09:55:01 PM
Quote from: Matilo Telephones on February 23, 2015, 04:33:32 PM
It does not ring, probably because you need to make a connection/bridge between the EW terminal (yellow) and A.

Is there diagram inside?

Yes, there is a diagram inside.  I'll take a closer look.  When you say a bridge, do you mean simply a wire going from one terminal to the other?

Yes, that's what he meant.

Be sure to look at your diagram to verify terminals,  according to my experience and diagrams, the bridge should be between EW and B, which are terminals #11 and 10.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: unbeldi on February 23, 2015, 10:19:46 PM
Quote from: Telephoner123 on February 23, 2015, 09:59:23 PM
Quote from: LarryInMichigan on February 23, 2015, 04:59:46 PM
My experience is that most of the transmitter capsules in those phones are noisy.  No amount of banging or tapping on them helps.  What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.

Is the capsule the sealed thing in the part that goes against your ear?  Would the resistor go in the handset?  or the main part of the phone?  I wasn't able to remove the capsule.

The transmitter is the microphone, the capsule that you speak into.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Matilo Telephones on February 24, 2015, 03:08:15 AM
Quote from: unbeldi on February 23, 2015, 10:08:06 PM
Quote from: Telephoner123 on February 23, 2015, 09:55:01 PM
Quote from: Matilo Telephones on February 23, 2015, 04:33:32 PM
It does not ring, probably because you need to make a connection/bridge between the EW terminal (yellow) and A.

Is there diagram inside?

Yes, there is a diagram inside.  I'll take a closer look.  When you say a bridge, do you mean simply a wire going from one terminal to the other?

Yes, that's what he meant.

Be sure to look at your diagram to verify terminals,  according to my experience and diagrams, the bridge should be between EW and B, which are terminals #11 and 10.
Quote from: unbeldi on February 23, 2015, 10:08:06 PM
Quote from: Telephoner123 on February 23, 2015, 09:55:01 PM
Quote from: Matilo Telephones on February 23, 2015, 04:33:32 PM
It does not ring, probably because you need to make a connection/bridge between the EW terminal (yellow) and A.

Is there diagram inside?

Yes, there is a diagram inside.  I'll take a closer look.  When you say a bridge, do you mean simply a wire going from one terminal to the other?

Yes, that's what he meant.

Be sure to look at your diagram to verify terminals,  according to my experience and diagrams, the bridge should be between EW and B, which are terminals #11 and 10.

There are 2 versions, with a different order to the A, B and EW terminals. I will post the diagrams.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Matilo Telephones on February 24, 2015, 03:10:15 AM
Here are the diagrams.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: dsk on February 24, 2015, 08:43:18 AM
Hi, and welcome!
It is always difficult to know at what level we should  star on when a new member comes in, My limitations are among others, limited English. I am not so good at making my phones look good enough, but I.m pretty good on solving problems, and making them working, sometimes by modifying, or making/using new parts.

I start this at a modest level, please tell if it is to easy, or if you want more specific details.

The ringer should work after connecting the 2 terminals 9-10 or 10-11 with a metallic wire.  (You have to test what your model you have)
Nothing may go wrong if you test the wrong alternative.

The transmitter or microphone capsule are under the mouthpiece cap.  The schematic tells me this is a transmitter with pretty small granulates, and may not easily be replaced by a capsule from e.g. a Western electric telephone who usually has higher quality transmitters. (no reason to not try if you have one)  Transmitters from Berman, Belgian , Dutch, or Italian +++ phones may often have equal data. Some European door telephone transmitters may also do the job.  Where has this (your grandfathers) phone been used?

dsk
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Jack Aman on February 24, 2015, 12:22:49 PM
What about electronic transmitters to replace the carbon grain microphones?  I have several, a couple a guy in Illinois made for me, and one I ordered from England.  They improve the outgoing voice performance of my 302's and 202's DRAMATICALLY.  Does anyone else here use them?
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: dsk on February 24, 2015, 01:36:18 PM
Yes many of them really makes the old phone work with modern sound, and may be the best way to get the family happy when using your old phones.  Many here seems to think it is a bad idea to put in electronics, but it is only a capsule easy to put back the original... if you keep it.  The circuitry of the phone in this thread may need to operate at extra low voltage, so may be difficult to find the right one.
German Ebay may come up with several if you search for: Sprechkapsel
(ebay.de)
some other links: http://www.elt24.de/shop/STR-80540-Mikrofon-fuer-Tuerstation-MK-1-
http://tinyurl.com/ml85tyw


dsk
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: unbeldi on February 24, 2015, 01:59:34 PM
I think this makes the most sense for old instruments such as the candlesticks. The transmitters in those, even if in excellent condition still, indeed have quite poor audio characteristics, often unacceptable for modern use.  Phoneco and probably others sell little integrated circuit boards that fit directly into the historical transmitter mount.  They use a low-voltage IC that is powered directly from the loop current.  But they add significantly to the cost of a restoration.

Later transmitters are plentiful in good quality.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: dsk on February 24, 2015, 02:25:02 PM
Most telephones used in the USA has had the close to the circuits used in W.E. 302, or 500 from 1960 to they stopped using carbon transmitter, and transmitters made for these are of an outstanding quality compared to most European capsules. The circuit in the diagrams in this thread shows a circuit where as much as 50% of the DC may escape trough the induction coils other windings, and we are left with a typical 2.5 volts or 12-15 milli-amps of current, this makes the transmitter from W.E. phone less suitable, and much of the electronic replacements will fail. This makes finding a suitable transmitter a little worse, but not impossible.  That's the reason for using smaller granulates than used in the typical WE T1  ???

dsk
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Telephoner123 on February 24, 2015, 07:51:16 PM
1.  I got the ringer working.  Many thanks!  It was surprisingly easy - just bridged 9 and 10.  I read the schematic, but I still don't understand why that works.  Could anyone explain?

2. 
Quote from: LarryInMichigan on February 23, 2015, 04:59:46 PM
What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.

Unfortunately, this part didn't work.  I even tried a 1.5k resistor and there was no difference.  But first I want to be sure I did it right.  I disconnected the red wire (I think it was #5, forgot to write it down) from the terminal strip.  Then I connected one end of the resistor and a small piece of wire each to the screw where the red wire was.  Next, I connected the other end of both to the horseshoe connector on the red wire.  I think the connection was good enough.

Does that sound correct?
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: unbeldi on February 24, 2015, 08:38:48 PM
Quote from: Telephoner123 on February 24, 2015, 07:51:16 PM
1.  I got the ringer working.  Many thanks!  It was surprisingly easy - just bridged 9 and 10.  I read the schematic, but I still don't understand why that works.  Could anyone explain?

Modern telephone lines have only two wires, called tip and ring; they carry voice, dialing pulses, and ringing current.  To make the phone ring its ringer is connected across these two wires.  But included in that ringer circuit has to be a capacitor, formerly called a condenser, which prevents a direct current (DC) short, and only permit alternating current (AC) to reach the ringer.  It used to be that the ringing current was not delivered via these wires, but required an additional connection to earth ground, so that the ringing circuit was between the 'ring' wire and ground, or the 'tip' wire and ground.  The proper connection was often made not inside the phone, but on the network interface of the incoming phone line, so that the line cord of the phone also had three wires.  When you bridged those two terminals you eliminated the ground wire and direct delivered ringing current from just tip and ring.  This is called bridged ringing.
If your line cord was still the original one, you might have been able to install the jumper on the other end of the cord.  One of my 1951s still had the original three-wire line cord and this was all I needed to do, for example.

Quote
2. 
Quote from: LarryInMichigan on February 23, 2015, 04:59:46 PM
What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.

Unfortunately, this part didn't work.  I even tried a 1.5k resistor and there was no difference.  But first I want to be sure I did it right.  I disconnected the red wire (I think it was #5, forgot to write it down) from the terminal strip.  Then I connected one end of the resistor and a small piece of wire each to the screw where the red wire was.  Next, I connected the other end of both to the horseshoe connector on the red wire.  I think the connection was good enough.

Does that sound correct?

The microphone is connected between points 5 and 6 in all cases, I believe. So, in order to try this recipe you would install the resistor ends on those two terminals as well.  A 1.5k resistor probably would have little effect, though, for the following reason:

R = ( 1/R1 + 1/R2 )-1

If R1 is the transmitter, and say its resistance is 100 ohms (a guess), and the R2 is your resistor of 1.5 kΩ, then the total resistance of  them in parallel is  about 94 Ω.    So your resistor is too large to have much of an effect.


Do you hear any static if you simply remove the transmitter? As dsk pointed out, these circuits maintain another current path that maintains the phone connection even without the transmitter and waste some current when present.  But this permits you to test whether it is in fact the transmitter creating the static.  I don't recall testing this myself right now, it may be that this does not create enough current flow in the telephone.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: LarryInMichigan on February 24, 2015, 08:44:07 PM
Quote from: Telephoner123 on February 24, 2015, 07:51:16 PM
1.  I got the ringer working.  Many thanks!  It was surprisingly easy - just bridged 9 and 10.  I read the schematic, but I still don't understand why that works.  Could anyone explain?

2. 
Quote from: LarryInMichigan on February 23, 2015, 04:59:46 PM
What may help is connecting a resistor (anywhere between 300 and 800Ω in parallel with the transmitter to shunt some of the current away from it.

Unfortunately, this part didn't work.  I even tried a 1.5k resistor and there was no difference.  But first I want to be sure I did it right.  I disconnected the red wire (I think it was #5, forgot to write it down) from the terminal strip.  Then I connected one end of the resistor and a small piece of wire each to the screw where the red wire was.  Next, I connected the other end of both to the horseshoe connector on the red wire.  I think the connection was good enough.

Does that sound correct?

It sounds like you connected a resistor in series instead of in parallel.  As unbeldi asked, do you hear static when the transmitter capsule is removed from the handset?  If so, the transmitter is not causing it.  There could be a loose connection somewhere and/or a dirty hook switch.  Dirty contacts on hook switches have been a source of static on a number pf my phones.

Larry
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: unbeldi on February 24, 2015, 08:50:20 PM
If you indeed installed the resistor in series with the transmitter, as Larry is suspecting, then I would say this also eliminates the transmitter from causing the static, because this would reduce the current through the transmitter to a tiny fraction of what it should be so that any kind of noise would also be rather small, and you should definitely be able to hear the difference.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Matilo Telephones on February 25, 2015, 06:02:27 PM
Quote from: unbeldi on February 24, 2015, 08:38:48 PM
Quote from: Telephoner123 on February 24, 2015, 07:51:16 PM
1.  I got the ringer working.  Many thanks!  It was surprisingly easy - just bridged 9 and 10.  I read the schematic, but I still don't understand why that works.  Could anyone explain?

Modern telephone lines have only two wires, called tip and ring; they carry voice, dialing pulses, and ringing current.  To make the phone ring its ringer is connected across these two wires.  But included in that ringer circuit has to be a capacitor, formerly called a condenser, which prevents a direct current (DC) short, and only permit alternating current (AC) to reach the ringer.  It used to be that the ringing current was not delivered via these wires, but required an additional connection to earth ground, so that the ringing circuit was between the 'ring' wire and ground, or the 'tip' wire and ground.  The proper connection was often made not inside the phone, but on the network interface of the incoming phone line, so that the line cord of the phone also had three wires.  When you bridged those two terminals you eliminated the ground wire and direct delivered ringing current from just tip and ring.  This is called bridged ringing.
If your line cord was still the original one, you might have been able to install the jumper on the other end of the cord.  One of my 1951s still had the original three-wire line cord and this was all I needed to do, for example.

Quote


Unfortunately, this part didn't work.  I even tried a 1.5k resistor and there was no difference.  But first I want to be sure I did it right.  I disconnected the red wire (I think it was #5, forgot to write it down) from the terminal strip.  Then I connected one end of the resistor and a small piece of wire each to the screw where the red wire was.  Next, I connected the other end of both to the horseshoe connector on the red wire.  I think the connection was good enough.

Does that sound correct?


[/quote]

That may be the case for some phones, but not for these Dutch phones.
They had to conform to technical specs laid down in the so called Norm 51 (1951) wich prescribed this lay out.
This was done, because the telephone needed to be able to be connected to an extra ringer, connected in series with the ringer in the telephone. All PTT phones had this untill well into the 80s.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Telephoner123 on February 26, 2015, 01:47:02 PM
Thanks for the additional advice about the transmitter.  I played around with a few different resistors connected across the 5 and 6 terminals.  One that's about 220 ohms seems to do the trick (about 10 ohms was dead, 550 still static).  My wife says it sounds like I'm "far away" when I talk on it.  But I assume that's inherent in this design.  It's certainly usable now.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: LarryInMichigan on February 26, 2015, 02:52:10 PM
Quote from: Telephoner123 on February 26, 2015, 01:47:02 PM
Thanks for the additional advice about the transmitter.  I played around with a few different resistors connected across the 5 and 6 terminals.  One that's about 220 ohms seems to do the trick (about 10 ohms was dead, 550 still static).  My wife says it sounds like I'm "far away" when I talk on it.  But I assume that's inherent in this design.  It's certainly usable now.

The reason that you sound "far away" is probably the resistor.  I have not been able to eliminate static from many of my transmitters without also attenuating the sound too much.  You may want to try replacing the transmitter with a T1 (Western Electric or similar).  You will probably still need a resistor because the T1 has more gain than transmitter for which the phone was designed.

Larry
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Telephoner123 on February 26, 2015, 04:00:43 PM
But how do you get the existing transmitter out?  I tried and it wouldn't budge
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: LarryInMichigan on February 26, 2015, 04:52:49 PM
t
Quote from: Telephoner123 on February 26, 2015, 04:00:43 PM
But how do you get the existing transmitter out?  I tried and it wouldn't budge
The transmitter will normally fall out when the cap is removed from the handset.  Was yours glued in place?

Larry
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: Matilo Telephones on February 26, 2015, 05:02:36 PM
The transmitter rests on a rubber/plastic ring inside the cap. They sometimes get stuck to it. Perhaps because of the glue with which the ring was glued, or because of the aging of that ring, which makes it sticky.

It usually pops out, if you use a screwdriver. Be carefull you do not damage the bakelite. Otherwise use something made of plastic or wood if you are not sure.

Heating it a little may loosen it. Not too hot, of course.
Title: Re: Troubleshooting PTT Ericsson 1951
Post by: ka1axy on August 17, 2021, 12:10:57 PM
Here's a third schematic, mine is wired differently than the other two schematics posted. Mine didn't ring, but dial and talk worked fine. It had an old US 4-pin plug on it with YEL and BLU on one pin and RED and GRN on the other.

Terminal strip was wired as:
9 - YEL (bell)
10 - BLU (b)[RING]
11 - RED (a)[TIP]
12 -
13 - GRN (gnd)[GND]

I rewired (to match Bell color code):
9 - BLU (bell)
10 - RED (RING)
11 - GRN (TIP)
12 -
13 - YEL (GND)

Then, on the 4-pin plug, I connected both BLU and RED to the RED pin.
All works as expected; rings, talks and dials. Slight static, which is tolerable.