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Help needed identifying this telephone.

Started by jonboysez, September 29, 2012, 07:45:01 PM

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twocvbloke

Generally phone systems are pretty much the same from country to country, some lines have differing voltages between countries, but ultimately the phones are usually universal... :)

One thing that could be an issue is the contacts inside the phone, they could be dirty, according to some instructions on here, running a piece of thin card through them can clean them and hopefully restore proper connectivity and maybe increase the volume, if not, it's probably just a case of the phone showing it's age...  :-\

dsk

Quote from: jonboysez on September 30, 2012, 05:29:43 PM
Tried the strap between L2 and T, and L2 and RT - neither made a louder dial tone. I definitely have a dial tone but it is very weak - maybe we are spoilt in the UK with a loud dial tone? I have an ericsson phone from Sweden and I can't get a loud dial tone on that either, and when I tried calling someone they could hardly hear me. I've not actually tried phoning anyone from this Standard phone but I suspect they will have trouble hearing me similarly. Just out of interest, do you know if any phone should work ok in any country, considering different voltages on the wire etc? Maybe some phones are incompatible on the UK network?

In this case, I would say no. The UK system has 2 major differences from what you find here (Norway) and whats common in USA/Canada. The ring cadence, with double rings, and the master socket with a common ringer capacitor. (Actually a good idea).

For us who really like the fetteling, your phone is a good project  :D  and the circuit design is extremely reliable and should work all over the world.  Before i understood the value of phones all Ericsson phones ended in the trash, to bad sound  :'(  so I actually have no Cobra  8)

The problem is it is quite many (but easy) things to sort out.
To start again:
To test the handset components and handset cord you could remove T and R from the terminals in the phone, and connect the line (or a 3.4-9 v battery) to the 2 wires. You should hear yourselves loud and clear. If changing polarity makes great difference in level, the receiver magnet may be weak. 

dsk

jonboysez

I'll give it a go when I'm back from work.

jonboysez

Oh heck - now that you mention Cobra, I bought this phone along with an Ericofon (Ohio badged) from the same seller - I've not opened that one yet, but was expecting that to be ok (I have a Post Office Property badged one from the UK and that works fine, tho the British ones don't have a bell/buzzer in them). I thought you was an American................just heard the result of the Rider Cup, ha ha how did we turn that around we were dead and buried!!

teka-bb

Quote from: LarryInMichigan on September 29, 2012, 10:13:55 PM
It looks like a very close relative to the Dutch PTT phone by Standard Electric.

Larry

The outside appearance of the phones are the same. Electrically they are (totally) different.

=============================================
Regards,

Remco, JKL Museum of Telephony Curator

JKL Museum of Telephony: http://jklmuseum.com/
=============================================
TCI Library: http://www.telephonecollectors.info/
=============================================

jonboysez

Hi DSK
Do you mean remove the wires from T and R terminals inside the phone then attach the red wire (from the socket) to one of these wires and the white wire to the other? Should that give me the dial tone in the receiver? Obviously if its louder it means some bad contact somewhere else in the signal's normal path through the phone?

dsk

I don't know the colors from your line, but probably, yes, this will send the current trough the receiver and transmitter in series, this makes the simplest working speech circuit I know.

dsk

jonboysez

Right that definitely made a difference - can now hear a dial tone, not quite as good as on modern phone but much better than it was - so that means some other contacts not clean? I have run an emery board (what women use to sand their nails with) between the contacts under the plunger but that doesnt seem to have made any difference. Anything else I can try to pinpoint where its not contacting?

twocvbloke

Quote from: jonboysez on October 01, 2012, 02:21:59 PMI have run an emery board (what women use to sand their nails with) between the contacts under the plunger but that doesnt seem to have made any difference. Anything else I can try to pinpoint where its not contacting?

That could have knackered them up, if you file away at the metal, you can bring on corrosion on the exposed metal, and ultimately the contacts will wear away sooner, hence why I mentioned running a piece of card through the contacts, as it's rough enough to clean, but smooth enough not to damage the metal... :-\

dsk

It is several possible things, defect capacitor, or something in the dial circuit.

I would start with the dial, remove all 4 wires from the dial, tape them and connect the line wires to
L1 and T.

dsk

jonboysez

Yes that worked! Removed the 4 wires from back of dial then attached line wires to L1 and T - got a good dial tone. So does that suggest its something wrong with the dial?

dsk

 :D Yes
We have isolated the problem.
1 does the colors of the 4 wires to the dial match with the diagram?
2 could you please post a picture of the dial back?

dsk

jonboysez

Just had a good look at the dial workings - think I can see something already not working right.  Looking from underneath the dial the contacts bit forms a U shape roughly. On the left side top there is a little plastic piece like an upside down U shape that I assume should locate in the cogs of the dial as it turns (and opens the contact on the left side) - looks like it should catch on the cogs as the dial returns to its starting place, but its not catching - I have moved it manually and it worked just the once - should there be a spring on it thats missing?

jonboysez

Made a few photos - the wires are attached to a piece of plastic that was cracked - I managed to attach the 4th wire ok by bending the loose plastic - note, these pictures are from the back of the wires so order is reversed if photographing them as attached tp the dial.

teka-bb


The metal spring on the left should be on the other side of the metal piece it's currently resting on. It should be against the screw that holds the 'forked' black piece. When the dial is in its starting position the pin on the black cog wheel should be resting against the metal spring on the right so it engages the contacts.

Let me know if the above is clear. If not I'll take a picture of one of my dials.
=============================================
Regards,

Remco, JKL Museum of Telephony Curator

JKL Museum of Telephony: http://jklmuseum.com/
=============================================
TCI Library: http://www.telephonecollectors.info/
=============================================