Extra wires on GPO 746? - UK Vintage Radio Repair and Restoration Discussion Forum

only1carra · 25th Oct 2011, 12:49 pm

Hi
Just completed my first ever GPO conversion and it works!
Over the moon about that, however I'm trying to convert another exactly the same.

This phone seems to have some extra wires related to where you put the handset down to end a call, one on the left side and one unit in the centre at the top just behind the dial, each unit has a few wires coming from it.

Can't get the phone to work and I'm pretty sure its something to do with these wires, any ideas

Thanks

julie_m · 25th Oct 2011, 1:32 pm

Can we have some pictures, please?

This may help you: N diagram 846

Basically, start by wiring it up like the diagram, leaving anything extraneous unconnected. Then: Unstrap T7 from T6 (park removed strap across an existing strap to prevent it from getting lost). Pin 2 of socket (red) to T8. Pin 3 of socket (blue) to T6. Pin 5 of socket (white) to T18. 3.3kΩ 0.5W resistor (or strap, if phone has been retro-fitted with 2 X 2kΩ bell coils) from T17 to T18. Pin 4 of socket (green) not used; if crimp terminal fitted, cover with insulating tape or attach to a spare terminal (T10, T11, T12, T13 all go nowhere). NB colours in line cord may not be as indicated, but pin 2 of the socket is the one nearest the latch.

AndiiT · 25th Oct 2011, 8:00 pm

Quote:

Originally Posted by only1carra

......This phone seems to have some extra wires related to where you put the handset down to end a call, one on the left side and one unit in the centre at the top just behind the dial, each unit has a few wires coming from it....

These sound like an Auxiliary gravity switch and an Auxiliary button. It's possible that the phone was originally used as an extension to a PBX so may be wired differently to what is required for use on a domestic exchange line, that said phones wired for PBX use aren't wired all that differently.

An alternative thought is that the phone was wired for shared service (party) line use - if that is the case you may have problems getting it to work on a present day exchange line without rewiring.

I would proceed as ajs has already suggested leaving any wires from the additional auxiliary units disconnected and tucked safely away.

Please try and post a picture for us as this will help us to help you a lot.

Regards

Andrew

25th Oct 2011, 12:49 pm	#1
only1carra Retired Dormant Member Join Date: Oct 2011 Location: Preston, Lancashire, UK. Posts: 44	Extra wires on GPO 746? Hi Just completed my first ever GPO conversion and it works! Over the moon about that, however I'm trying to convert another exactly the same. This phone seems to have some extra wires related to where you put the handset down to end a call, one on the left side and one unit in the centre at the top just behind the dial, each unit has a few wires coming from it. Can't get the phone to work and I'm pretty sure its something to do with these wires, any ideas Thanks Last edited by Station X; 25th Oct 2011 at 12:53 pm. Reason: ims and cants

25th Oct 2011, 1:32 pm	#2
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: extra wires on GPO 746???? Can we have some pictures, please? This may help you: N diagram 846 Basically, start by wiring it up like the diagram, leaving anything extraneous unconnected. Then: Unstrap T7 from T6 (park removed strap across an existing strap to prevent it from getting lost). Pin 2 of socket (red) to T8. Pin 3 of socket (blue) to T6. Pin 5 of socket (white) to T18. 3.3kΩ 0.5W resistor (or strap, if phone has been retro-fitted with 2 X 2kΩ bell coils) from T17 to T18. Pin 4 of socket (green) not used; if crimp terminal fitted, cover with insulating tape or attach to a spare terminal (T10, T11, T12, T13 all go nowhere). NB colours in line cord may not be as indicated, but pin 2 of the socket is the one nearest the latch. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.