Ericsson 706-clone - help identifying a switch and component - UK Vintage Radio Repair and Restoration Discussion Forum

whereistom · 19th Jul 2012, 7:42 am

I've just got an Ericsson N1904 A270 (706 clone) - one of these http://www.britishtelephones.com/ericsson/n1904.htm
Excitingly, it has it's original box - so I know that it was a British Railways telephone.

It has 2 buttons on top, one of which operates a switch that I can't find reference to (It certainly doesn't look like anything on http://www.britishtelephones.com/switch1.htm). Also there is a mysterious component I've not seen before. I'd be interested to find out what both of these things are.

I have converted the phone ok - except the bells ding when picking up and putting down the receiver. I wonder if this is related to the mystery component.

The switch (first photo) has no part number or other markings on it that I can see. It six wires coming out, which go to the following terminals:
Orange - 6
Brown - 19
Grey - 18
Blue - 7
Green - 4
White with blue stripe - 15

There is a second switch which disengages this one, and it also disengages when you hang up.

The large silver component (second photo) is directly connected between terminals 18 and 19. It has a green wire coming out the back going to a component further back in the phone.
Printed on it is:
5910-99-
011-9827
0-1 uF±25%
200vat 100.C
B5000KZ
AHC/XE

I'm guessing it's a capacitor (my electronics knowledge is pretty much non-existant though, so shoot me down if I'm wrong!) but I've no idea why it would be there.

Photos attached of both. Anybody know what they are, what they're doing in there, and whether they're causing the bell to ding?

dagskarlsen · 19th Jul 2012, 9:42 am

This tinkle problem may be solved by simply reverse polarity on the line (works sometimes).
OR
Adjusting, or putting in a bias spring forsing the hammer to rest at one side.
OR
Putting in an electronic component in series with the ringer. E.G a quadrac, or a pair of Zener diodes.

It's probably nothing wrong with your modification.

dsk

AndiiT · 19th Jul 2012, 8:23 pm

Hi,
This has probably been part of an Ericsson/Plessey "Manager/Secretary" Plan system similar to the GPO Planset 625

The additional switches are for routing the exchange line to an associated extension phone and the additional component is an extra capacitor for bell transfer purposes.

Some information about the Ericsson plan systems can be found here

The diagrams for these can be difficult to obtain although I have a small number of them which may be of use to you, just PM me if you require them.

If you just want to use the phone without the additional switches wire as shown on the instructions for the GPO/BT 706 shown here leaving the additional switches out of circuit.

Incidentally the N1906 isn't a clone of the 706, it's the other way round!

Regards

Andrew

whereistom · 20th Jul 2012, 10:19 pm

Andrew -
"Incidentally the N1906 isn't a clone of the 706, it's the other way round!"
How interesting, I didn't know that! Learn something new every day

Thanks for the info - I had wondered if it was some sort of plan system, as it presumably came from a railway station.

I'm more interested in it as a phone, so have disconnected the switch - but left it in place with the wires in some electrical tape, in case I or anyone else wants to restore it's full planset glory in the future!

dagskarlsen -
I've fixed the tinkle by wiring in a Thermistor 1A, which I'd coincidentally ordered for another phone and arrived today. Works like a charm, although it means I'll have to buy another one now!

AndiiT · 20th Jul 2012, 10:56 pm

Hi again,
All the GPO 700 series phones were manufactured by other suppliers such as Ericsson, Ferranti, PYE and GEC (these were the main four suppliers but there may have been others)

If the phone is wired correctly you shouldn't experience any bell tinkle even without a thermistor fitted although if you have any ADSL filters on your line it may be these that are causing the tinkling issue and not the phone itself - you could prove this by connecting your phone direct to the main incoming Line jack test socket after removing the faceplate.

It is possible to wire these phones so that the exchange line is only connected when one of the buttons is depressed, the switch hook latch plate disengaging the buttons when the receiver is placed on its rest as you have already found out.

Just to confirm, the wires in your telephone, when wired as a standard phone, should be as follows -

Handset
RED T1
GREEN T2
BLUE T3
WHITE T10

STRAPS
3K3 Resistor between T4 - T5
T5 - T6
T16 - T17 - T18 - T19

LINE CORD
WHITE T18
RED T8
BLUE T5
GREEN T15 (Spare)

Regards

Andrew

19th Jul 2012, 7:42 am	#1
whereistom Retired Dormant Member Join Date: Feb 2010 Location: Manchester Posts: 25	Ericsson 706-clone - help identifying a switch and component I've just got an Ericsson N1904 A270 (706 clone) - one of these http://www.britishtelephones.com/ericsson/n1904.htm Excitingly, it has it's original box - so I know that it was a British Railways telephone. It has 2 buttons on top, one of which operates a switch that I can't find reference to (It certainly doesn't look like anything on http://www.britishtelephones.com/switch1.htm). Also there is a mysterious component I've not seen before. I'd be interested to find out what both of these things are. I have converted the phone ok - except the bells ding when picking up and putting down the receiver. I wonder if this is related to the mystery component. The switch (first photo) has no part number or other markings on it that I can see. It six wires coming out, which go to the following terminals: Orange - 6 Brown - 19 Grey - 18 Blue - 7 Green - 4 White with blue stripe - 15 There is a second switch which disengages this one, and it also disengages when you hang up. The large silver component (second photo) is directly connected between terminals 18 and 19. It has a green wire coming out the back going to a component further back in the phone. Printed on it is: 5910-99- 011-9827 0-1 uF±25% 200vat 100.C B5000KZ AHC/XE I'm guessing it's a capacitor (my electronics knowledge is pretty much non-existant though, so shoot me down if I'm wrong!) but I've no idea why it would be there. Photos attached of both. Anybody know what they are, what they're doing in there, and whether they're causing the bell to ding? Attached Thumbnails

19th Jul 2012, 9:42 am	#2
dagskarlsen Heptode Join Date: Jan 2008 Location: Hakadal, Norway Posts: 643	Re: Ericsson 706-clone - help identifying a switch and component This tinkle problem may be solved by simply reverse polarity on the line (works sometimes). OR Adjusting, or putting in a bias spring forsing the hammer to rest at one side. OR Putting in an electronic component in series with the ringer. E.G a quadrac, or a pair of Zener diodes. It's probably nothing wrong with your modification. dsk

19th Jul 2012, 8:23 pm	#3
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: Ericsson 706-clone - help identifying a switch and component Hi, This has probably been part of an Ericsson/Plessey "Manager/Secretary" Plan system similar to the GPO Planset 625 The additional switches are for routing the exchange line to an associated extension phone and the additional component is an extra capacitor for bell transfer purposes. Some information about the Ericsson plan systems can be found here The diagrams for these can be difficult to obtain although I have a small number of them which may be of use to you, just PM me if you require them. If you just want to use the phone without the additional switches wire as shown on the instructions for the GPO/BT 706 shown here leaving the additional switches out of circuit. Incidentally the N1906 isn't a clone of the 706, it's the other way round! Regards Andrew

20th Jul 2012, 10:19 pm	#4
whereistom Retired Dormant Member Join Date: Feb 2010 Location: Manchester Posts: 25	Re: Ericsson 706-clone - help identifying a switch and component Andrew - "Incidentally the N1906 isn't a clone of the 706, it's the other way round!" How interesting, I didn't know that! Learn something new every day Thanks for the info - I had wondered if it was some sort of plan system, as it presumably came from a railway station. I'm more interested in it as a phone, so have disconnected the switch - but left it in place with the wires in some electrical tape, in case I or anyone else wants to restore it's full planset glory in the future! dagskarlsen - I've fixed the tinkle by wiring in a Thermistor 1A, which I'd coincidentally ordered for another phone and arrived today. Works like a charm, although it means I'll have to buy another one now!

20th Jul 2012, 10:56 pm	#5
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: Ericsson 706-clone - help identifying a switch and component Hi again, All the GPO 700 series phones were manufactured by other suppliers such as Ericsson, Ferranti, PYE and GEC (these were the main four suppliers but there may have been others) If the phone is wired correctly you shouldn't experience any bell tinkle even without a thermistor fitted although if you have any ADSL filters on your line it may be these that are causing the tinkling issue and not the phone itself - you could prove this by connecting your phone direct to the main incoming Line jack test socket after removing the faceplate. It is possible to wire these phones so that the exchange line is only connected when one of the buttons is depressed, the switch hook latch plate disengaging the buttons when the receiver is placed on its rest as you have already found out. Just to confirm, the wires in your telephone, when wired as a standard phone, should be as follows - Handset RED T1 GREEN T2 BLUE T3 WHITE T10 STRAPS 3K3 Resistor between T4 - T5 T5 - T6 T16 - T17 - T18 - T19 LINE CORD WHITE T18 RED T8 BLUE T5 GREEN T15 (Spare) Regards Andrew