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Fixing my Polish-assembled pre-war Ericsson

Started by IIfx, November 13, 2013, 05:33:37 PM

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IIfx

Well, after 3 months of being busy with College work, I thought I would attack the problems present in this phone before winter break. Here is a rundown of the trouble-symptoms:

-What Works-
Rings when calls are received on the line (very loud!)
Hook switch functions normally
Rotary dial is extremely smooth, can dial out correctly.

-What doesnt work-
No sound from the headset
When headset is off the hook switch, causes the phone line to drop in volume drastically. Does not kill the connection on other phones, just makes the dial tone very quiet. When dialing, you can hear very loud clear pulses as well as momentary dial tone, before it fades back (from another phone).

-Testing Procedure-
Line cord has been found faulty - temporarily rigged using the modular jack from the WEco 2500.
Went through and cleaned all electrical contacts with contact cleaner

-Photos-
Inside of phone:

Schematic provided by dsk in an earlier thread (thanks!):


To be honest, I dont know where to begin testing otherwise. I have a theory that the line cord to the headset is bad as well, and I can try getting another to replace it with. I could probably hack on the 2500s modular headset by moving the jack from the 2500 and connecting it to the Ericsson to see if that causes calls to come in clear, but I dont know if the WE receiver and microphone are compatible with the network in the Ericsson. The problem of the phone lowering the volume on the entire line is also interesting...no idea where to start with that (bad capacitor? this phone has a big rectangular one inside.)

Looking forward to getting this working....after that I will move on to my ill touch-tone trimline.  :)

--------------------

EDIT:  Photo downloaded and re-posted as a forum attachment for posterity


Jack Ryan

Well, gotta start somewhere...

It sounds like a problem with the handset.

Remove the transmitter element.
Does the phone still load the line when the handset is lifted?
If you lift the handset of another working telephone that is connected to the same line, can you hear dial tone in the phone under test?

If no change, disconnect the handset cable from the telephone.
Does the phone still load the line when the handset is lifted?

If no change, check the wiring of the induction coil (IC). Can the IC be disconnected at point 1 on the schematic (lower diagram) – either at the IC or the dial? Does the phone still load the line when the handset is lifted?

If no change with the IC disconnected, there is a wiring or component problem around the bell, capacitor and dial. I doubt that this is the case though because you can dial out.

Good luck.
Jack

G-Man

First, take out the earpiece element from the 2500-set and temporarily connected it to terminals "2" and "4" to see if you can then hear dial-tone. Then try it at the end of the wires for the earpiece at the end of the HANDSET cord to eliminate it as being the problem.

Also, this model may have an inherent design problem of excessively loading down the line. However, disconnect the RED wire for the transmitter at terminal "6." This will help determine if the transmitter is faulty.

With it disconnected you should see a nominal 632-ohms across the line. The condenser should not be the problem.

dsk

#3
Hi again.
Most likely the diagram is the correct one, but some variations are actually made.
Any way we can simplify it to this circuit, and one more like the Antwerp telephone described in other threads.

If you just remove all 3 cords to the handset, the other circuit should not engage the line when going off-hook.

The handset may be tested by just connect a battery of 3-9V (very tolerant voltage span)(, or direct to telephone line) the cords red and yellow. If you may hear yourselves, the handset with elements and cord are OK.

The telephone should work this way with no handset connected. (Handset resting on hook-sw.)  Ringing as normal. Lifting the handset, and the telephone engages the line (But of-course no sound in and out via the non-connected handset).
Lifting handset, waiting a little, and dialing, and it should ring another phone, (still no sound) .

The receiver are usually of a type with a removable diaphragm, If this one is lost you will need a replacement. if so: In the mean time, a thin sheet of iron solves it surprisingly well, The thin poop used on calendars with a magnetic ring to move from day to day seems perfect, and you may cut it with regular scissors. (It maybe a little stressing for the scissors)

The transmitter capsule could be a little worse, but many other makes use the same size, including door-telephones.

The cord just requires 3 cords, lent from whatever you have, and finds suitable.

dsk

PS more here: http://tinyurl.com/n49rz3g   DS

IIfx

#4
Thank you everyone for the advice, I have some progress. After disconnecting the handset, I noticed the phone was no longer killing the volume on the line. Even after reconnecting it, it did not kill volume on the line...weird! The phone now functionally works, I can hear dial tone or conversations, and people can hear me.

The issues have shifted a bit. Volume from the receiver is quiet, my WE 2500 and 500 are almost 3x as loud on a call.  If another phone on the line is picked up, the Ericsson will lightly ring. Even funnier, if you dial the WE 500 with the Ericsson hung up, the Ericsson will lightly ring to the pulse dialing of the 500.  Transmission is ok, according to people I called.

Something is still off, but at least it works somewhat now.  :)

LarryInMichigan

It could be that the connectors on the handset wires were touching each other before you disconnected them.  The receiver probably has a steel diaphragm.  If so, it will never sound as good as the ones on your 500 or 2500, and it may be weak.  The magnet may be a bit weak and/or the diaphragm may be too tight/loose or near/far from the coil.  Fiddling with it might improve the loudness.

The 'tinkling' of the ringer when another phone is taken off-hook or dialed is normal.  The ringer does not have a bias spring, like North American models, to prevent small line voltage changes from causing the clapper to move.  Adjusting the gongs and/or reversing the L1 and L2 wires may help.

Larry

dsk

#6
My receiver has a reasonable sound. Here are some pictures.
The diaphragm has a relatively small gap to the electromagnet. (Easy to push to touch)
Sometimes they was touching, and then adjusted by putting in a thin paper ring under the diaphragm.

dsk