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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment

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Old 21st Mar 2010, 9:50 pm   #41
Chris450d
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Default Re: GPO 706 dead

So would this affect the strap on T8 - T9 where the bell capacitor lies?
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Old 22nd Mar 2010, 2:25 pm   #42
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Default Re: GPO 706 dead

If using the internal capacitor (two-wire working), T8-T9 need to be strapped, as do T6-T7. When using an external capacitor with three-wire working, one or the other (usually the latter) needs to be unstrapped, with the bell lead going to T6.
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Old 22nd Mar 2010, 3:52 pm   #43
Chris450d
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Default Re: GPO 706 dead

Another update:

With the following terminals ONLY strapped:

T6-T7, T8-T9
T16 - T17 - T18 - T19

and line cord wires as follows:

White to T18
Red to T6
Blue to T4
Green unknown!

I managed to operate the bell and speaker!
So to recap, the phone rings when being called. The caller is heard but I cannot speak back!

It seems the wiring has really nothing to do with the original conversion wiring! Any help as to how to get the Mic to work?

Cheers! looks like I'm soon there
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Old 27th Mar 2010, 6:46 pm   #44
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Default Re: GPO 706 dead

You MASTER jack has only terminals (J5 A Leg positive and J2 B leg negative) connected. Check the polarity with your meter. Is it correct?

One pair of wires obviously goes to the exchange. I assume the other pair goes to the EXTENSION sockets?

If wired as per the UK system the EXTENSION sockets should have NO components on the printed circuit board except the actual jack and J2, J3 and J5 on all jacks should be wired together.

As things stand, so long as the polarity is correct, your 706 should work as a three wire extension if the conversion details are followed correctly and it is connected to the MASTER jack.

If wired to diagram N806 with the addition of a strap between T17 and T18, white of line cord to T16 and red of line cored to T8 it will work as a two wire extension in ANY jack.
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Old 27th Mar 2010, 6:56 pm   #45
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Default Re: GPO 706 dead

The microphone cannot possibly work without a connection from T8 to line (red of line cord) as it will have no DC flowing through it!
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Old 5th May 2010, 4:27 pm   #46
Pellseinydd
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Default Re: GPO 706 dead

the Tele 7P was if I remember correctly made by AEP (Portuguese subsiduary of Plessey). It was based on a 706 case but had no induction coil - just a resistor network - hence there being no regulator. It was designed for use on PAX's. Not seen one since my days with Plessey Comms Systems back in the 1980's.

Last edited by Darren-UK; 6th May 2010 at 8:31 am. Reason: Call got cut off.
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