GPO 706 in trouble. - UK Vintage Radio Repair and Restoration Discussion Forum

SeanStevens · 30th Nov 2009, 8:30 pm

I have a 706 that has not been converted to the little six contact plug. It has 5 wires going to an old GPO wall box.

No matter how I connect the wires to the new style wall box I get no proper results - just a high speed clicking sound.

So far I have worked the following out (although I know there are sites full of this info, my 'problem' may be recognised by readers here).

T18 = White = Position 2 on new plug
T 8 = Red = Position 5 on new plug
T 6 = Blue = Position 4 on new plug
T15 = Green = Position 3 on new plug
(or T17 as it was on the 706)

Is the phone broken - or does this look wrong to you?

SEAN

Nickthedentist · 30th Nov 2009, 8:34 pm

Hi Sean,

Could you post a good pic of the board as you've got it wired, please?

Nick.

SeanStevens · 30th Nov 2009, 8:46 pm

Photo as requested:

SEAN

Nickthedentist · 30th Nov 2009, 10:05 pm

OK, Sean, this doesn't seem to have been "converted" yet.

Start by removing the straps linking T6-T7 and T8-T9, and instead fit them between T5-T6 and T17-T18.

Your pic's not 100% clear; could you tell us the order of the coloured wires in the line cord, please?

Then get back to us

AndiiT · 30th Nov 2009, 11:24 pm

Hi,
Check Here for details of how to convert your 706 to Plug and socket working.

Regards
Andrew

SeanStevens · 1st Dec 2009, 9:57 am

No, I think you are right in that it has not had these mods made - I will do this tonight. BUT, there is no mention of the orange wire....... Polite suggestions please as to where to stick it!

SEAN

Nickthedentist · 1st Dec 2009, 11:57 am

The answer, Sean, is to "park" it on one of the unused terminals, i.e. T11 to T14.

The green wire is similarly redundant, and is conventionally connected to T15.

Nick.

SeanStevens · 2nd Dec 2009, 8:40 am

Well, it now has been converted - still does not work!!! I can hear the (unfiltered) ADSL on the line, but no dial tone. When I dial I get silence, then a beep, but it does not dial out of the house.

Next steps?

SEAN

russell_w_b · 2nd Dec 2009, 9:35 am

Quote:

Originally Posted by SeanStevens

Next steps?

Disconnect your telephone from its lead and plug. Connect an audio output from a wireless or other music source (or an audio oscillator output at about neg. 10db WRT 1mW at 600 Ohms) to terms: 8 and 18 in your telephone.

Can you hear the audio through your receiver? Does the audio cut off when you replace the handset?

Do this then report back.

russell_w_b · 2nd Dec 2009, 2:28 pm

Couple other things, assuming your telephone passes the 'music' test, as I described earlier:

Double-check your wiring to ensure that terminal 2, 3 and 5 in your LJU telephone socket go to term. 8, 6 and 18 respectively, in your telephone. The corresponding BT plug will be terminals 5, 4 and 2 looking at the contacts with the release-clip on the RHS (ie: a reversal of the socket terminal numbers - the BT plug reads 1-2-3-4-5-6 left-to-right with 1 and 6 not normally used).
Ensure you have links between terms: 8-9; 5-6; 16-17-18-19 and a 3, or a 3k3 resistor between terms. 4 and 5. There should be no links elsewhere.
Remove the plug-in regulator and clean the contacts, both ends.
Short out the microphone (terms: 3, 10) and measure the resistance, off hook, between terms: 8 and 18 (red and white connections, or 2 and 5 to your LJU - socket numbers!). You should see something like 25.5 Ohms with the regulator in-circuit, or 19 Ohms with the regulator shorted out (reversed).
With your meter across terms: 8 and 18 and the microphone still clipped out (terms: 3, 10), turn the dial and release it. You should either see something like 22 Ohms or a short-cct, depending on whether the dial-off normal contact is right across the incoming line, or whether it is shorting the microphone out. There were two arrangements, and Note 'F' on 'N'-diagram 806 refers.

I notice that your 706 had several other coloured wires connected. Are there any auxiliary switches on your telephone?

SeanStevens · 2nd Dec 2009, 4:31 pm

No, there are no extra switches or buttons on this 706.

I'll try these tests asap tonight, although I know the phone does not have the resistory thingy between terminals 4 and 5. More later, thanks for the help.

SEAN

russell_w_b · 2nd Dec 2009, 4:49 pm

Quote:

Originally Posted by SeanStevens

I know the phone does not have the resistory thingy between terminals 4 and 5.

Just use a link between terms 4 and 5 for now; it'll be fine.

Another test you can do is to connect a battery (4.5 - 12V will do) across terms. 8 and 18 and blow into the microphone. Can you hear yourself in the receiver? Does it crackle?

The reason I suggested shorting out the mic in the earlier test is that the resistance of the carbon mic varies with position and DC bias current, and you won't get a steady reading, hence the separate test above.

SeanStevens · 2nd Dec 2009, 6:17 pm

Quote:

Originally Posted by russell_w_b, in Post#9

Can you hear the audio through your receiver? Does the audio cut off when you replace the handset?

Do this then report back.

The audio is audible within the headset - and goes when the buttons are depressed.....

I don't know what this proves, but it seems to have passed.

SEAN

russell_w_b · 2nd Dec 2009, 6:55 pm

Quote:

Originally Posted by SeanStevens

I don't know what this proves, but it seems to have passed.

It proves that you can receive speech; that your ASTIC isn't bust. You'll need to run through the more, er, 'scientific' tests with an ohm-meter, as I later described.

Before you do that, though, connect a battery to 8 and 18 and see if your mic is working.

SeanStevens · 2nd Dec 2009, 7:19 pm

With a battery on 8 and 18 I got nothing from the speaker to earpiece.... I changed the mouthpiece for a known good spare....... Still nothing.

This doesn't look good - the detective work is slow with me doing the tests!

SEAN

SeanStevens · 2nd Dec 2009, 7:21 pm

I have no strap between terminals 8 and 9 - but neither does this:

http://www.britishtelephones.com/tranchan.htm#converted

I'll try one

SEAN

russell_w_b · 2nd Dec 2009, 7:33 pm

Quote:

Originally Posted by SeanStevens

I have no strap between terminals 8 and 9 - but neither does this:

http://www.britishtelephones.com/tranchan.htm#converted

I'll try one

SEAN

No need: this one doesn't matter - it's only for a capacitor you won't be using - should've said; tch!

Is your regulator OK? - The little card that slides into the slot beneath the cradle-switch? Reverse it (up-end it) and see if you get any side-tone with the battery test. Still with the battery test, and with T8 to T10 connected directly together (strapping out the dial-contacts), see if you can hear yourself.

If you can, it's your dial pulse contacts that are O/C.

SeanStevens · 2nd Dec 2009, 9:02 pm

I didn't realise that was removeable!!!

Changed it top to bottom - battery test is bad with it in either orientation.....

Frustrating this!!!

SEAN

russell_w_b · 2nd Dec 2009, 10:21 pm

Have you tried doing the battery test with T8 and T10 shorted together yet?

russell_w_b · 3rd Dec 2009, 9:25 am

...And don't forget to check the continuity of your mic wires from telephone to handset as well!

30th Nov 2009, 8:30 pm	#1
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	GPO 706 in trouble. I have a 706 that has not been converted to the little six contact plug. It has 5 wires going to an old GPO wall box. No matter how I connect the wires to the new style wall box I get no proper results - just a high speed clicking sound. So far I have worked the following out (although I know there are sites full of this info, my 'problem' may be recognised by readers here). T18 = White = Position 2 on new plug T 8 = Red = Position 5 on new plug T 6 = Blue = Position 4 on new plug T15 = Green = Position 3 on new plug (or T17 as it was on the 706) Is the phone broken - or does this look wrong to you? SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't. Last edited by Darren-UK; 2nd Dec 2009 at 3:29 pm. Reason: Title change. There's no such thing as a 'BT 706'.

30th Nov 2009, 8:34 pm	#2
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,839	Re: BT 706 in Trouble Hi Sean, Could you post a good pic of the board as you've got it wired, please? Nick.

30th Nov 2009, 8:46 pm	#3
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: BT 706 in Trouble Photo as requested: SEAN Attached Thumbnails __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

30th Nov 2009, 10:05 pm	#4
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,839	Re: BT 706 in Trouble OK, Sean, this doesn't seem to have been "converted" yet. Start by removing the straps linking T6-T7 and T8-T9, and instead fit them between T5-T6 and T17-T18. Your pic's not 100% clear; could you tell us the order of the coloured wires in the line cord, please? Then get back to us

30th Nov 2009, 11:24 pm	#5
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: GPO 706 in trouble. Hi, Check Here for details of how to convert your 706 to Plug and socket working. Regards Andrew

1st Dec 2009, 9:57 am	#6
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: GPO 706 in trouble. No, I think you are right in that it has not had these mods made - I will do this tonight. BUT, there is no mention of the orange wire....... Polite suggestions please as to where to stick it! SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

1st Dec 2009, 11:57 am	#7
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,839	Re: GPO 706 in trouble. The answer, Sean, is to "park" it on one of the unused terminals, i.e. T11 to T14. The green wire is similarly redundant, and is conventionally connected to T15. Nick.

2nd Dec 2009, 8:40 am	#8
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: GPO 706 in trouble. Well, it now has been converted - still does not work!!! I can hear the (unfiltered) ADSL on the line, but no dial tone. When I dial I get silence, then a beep, but it does not dial out of the house. Next steps? SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't. Last edited by SeanStevens; 2nd Dec 2009 at 8:41 am. Reason: spelling error

2nd Dec 2009, 2:28 pm	#10
russell_w_b Dekatron Join Date: Jul 2007 Location: Penrith, Cumbria, UK. Posts: 3,687	Re: GPO 706 in trouble. Couple other things, assuming your telephone passes the 'music' test, as I described earlier: Double-check your wiring to ensure that terminal 2, 3 and 5 in your LJU telephone socket go to term. 8, 6 and 18 respectively, in your telephone. The corresponding BT plug will be terminals 5, 4 and 2 looking at the contacts with the release-clip on the RHS (ie: a reversal of the socket terminal numbers - the BT plug reads 1-2-3-4-5-6 left-to-right with 1 and 6 not normally used). Ensure you have links between terms: 8-9; 5-6; 16-17-18-19 and a 3, or a 3k3 resistor between terms. 4 and 5. There should be no links elsewhere. Remove the plug-in regulator and clean the contacts, both ends. Short out the microphone (terms: 3, 10) and measure the resistance, off hook, between terms: 8 and 18 (red and white connections, or 2 and 5 to your LJU - socket numbers!). You should see something like 25.5 Ohms with the regulator in-circuit, or 19 Ohms with the regulator shorted out (reversed). With your meter across terms: 8 and 18 and the microphone still clipped out (terms: 3, 10), turn the dial and release it. You should either see something like 22 Ohms or a short-cct, depending on whether the dial-off normal contact is right across the incoming line, or whether it is shorting the microphone out. There were two arrangements, and Note 'F' on 'N'-diagram 806 refers. I notice that your 706 had several other coloured wires connected. Are there any auxiliary switches on your telephone? __________________ Regds, Russell W. B. G4YLI.

2nd Dec 2009, 4:31 pm	#11
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: GPO 706 in trouble. No, there are no extra switches or buttons on this 706. I'll try these tests asap tonight, although I know the phone does not have the resistory thingy between terminals 4 and 5. More later, thanks for the help. SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

2nd Dec 2009, 7:19 pm	#15
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: GPO 706 in trouble. With a battery on 8 and 18 I got nothing from the speaker to earpiece.... I changed the mouthpiece for a known good spare....... Still nothing. This doesn't look good - the detective work is slow with me doing the tests! SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

2nd Dec 2009, 7:21 pm	#16
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: GPO 706 in trouble. I have no strap between terminals 8 and 9 - but neither does this: http://www.britishtelephones.com/tranchan.htm#converted I'll try one SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

2nd Dec 2009, 9:02 pm	#18
SeanStevens Octode Join Date: Sep 2009 Location: Bath, Somerset, UK. Posts: 1,033	Re: GPO 706 in trouble. I didn't realise that was removeable!!! Changed it top to bottom - battery test is bad with it in either orientation..... Frustrating this!!! SEAN __________________ There are only 10 types of people, those who understand the binary system, and those who don't.

2nd Dec 2009, 10:21 pm	#19
russell_w_b Dekatron Join Date: Jul 2007 Location: Penrith, Cumbria, UK. Posts: 3,687	Re: GPO 706 in trouble. Have you tried doing the battery test with T8 and T10 shorted together yet? __________________ Regds, Russell W. B. G4YLI.

3rd Dec 2009, 9:25 am	#20
russell_w_b Dekatron Join Date: Jul 2007 Location: Penrith, Cumbria, UK. Posts: 3,687	Re: GPO 706 in trouble. ...And don't forget to check the continuity of your mic wires from telephone to handset as well! __________________ Regds, Russell W. B. G4YLI.