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Old 6th Mar 2018, 7:28 pm   #1
absolutelynice
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Default 706 Phone Conversion Help

Hi all,

I have a 706 phone I am trying to convert but there's a couple of wires I'm a bit unsure about. I've watched a few videos on YouTube for converting 746 phones but none that have the on/off switch like mine does.

I just wondered if anybody could possibly help me with this please as I've also looked at a few diagrams online but they're all very confusing. I'm a complete novice with this sort of thing and have very little understanding about these sorts of things unfortunately.

I've attached a photo at the bottom to show the phone as it is but here's the issues...

I have an orange cable, possibly coming from the bell, loose and hovering over T2 which I'm not sure where to put?

There are also blue (not connected), brown (connected to T13) and grey (connected to T16) cables which appear to come from the on/off switch that again, I'm not sure if they're in the correct locations?

There's also another orange cable, possibly from the bell at T16 which I'm not sure is in the correct location?

If anybody is able to help it would be greatly appreciated!

Many thanks in advance!
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Old 6th Mar 2018, 9:21 pm   #2
Dave Moll
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Default Re: 706 Phone Conversion Help

There will be three wires coming from the on/off switch (as you say coloured brown, blue and slate - i.e. grey), which is a two-way switch. I don't remember off-hand which is which, but one will be the common, which will be connected to one on the "off" position and the other in the "on" position.

The use of this switch is entirely optional, but if you wish to use it to switch the ringer on and off (the purpose for which it would originally have been intended), you will need to connect the two wires that are connected in the "on" position in series with the ringer.

In a non-converted 'phone it is likely that the switch would have been wired in parallel with the ringer to short it out in the "off" position. Assuming this to be the case, remove both the orange wire from the ringer, and the slate wire from the switch from T16, and move the ringer wire to T13, along with one of the two switch wires identified above, and move the other wire identified above to T16.

The wiring will otherwise be the same as that given here.
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Old 7th Mar 2018, 6:43 pm   #3
absolutelynice
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Default Re: 706 Phone Conversion Help

Thanks Dave, I'll give it a go this weekend.

I've also been told I need a 205 rectifier between T1 and T2 to stop the pops but a 1N series diode should do it. Does that sound about right?
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Old 7th Mar 2018, 8:22 pm   #4
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Default Re: 706 Phone Conversion Help

Be aware that the purpose of a 205 (which is actually two diodes in parallel with opposite polarity) is not to rectify, but (using the fact that the diodes will only [semi-]conduct above a threshold voltage) to damp the high-voltage pulses while allowing speech though unimpeded.

I'm not sufficiently up on semiconductor specifications to say whether 1N series will have the right characteristics, but assuming they do, you will need a pair as described above.

I would not, however, be too worried about fitting such a device if not already present. The 'phone should work fine without it.
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Old 7th Mar 2018, 10:47 pm   #5
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Default Re: 706 Phone Conversion Help

A couple of 1N400* whatever you have back-to-back will work fine as a noise clipper. Telephones with efficient rocking armature receivers like the 706 will provide quite an audible POP! on your ear if pressed against the receiver.

If the dial off-normal contacts are set up correctly they will shunt any receiver clicks when dialling, but the diodes will shunt off any pops if you happen to press the cradle switch when the receiver is against your ear.
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Old 11th Mar 2018, 6:16 pm   #6
absolutelynice
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Default Re: 706 Phone Conversion Help

Hi all,

Back with this again sorry as I'm still a bit confused.

I've attached a photo of where the slate, blue and brown wires attach to on the on/off switch.

It's not very clear from the photo but there are little N.C. and N.O. labels on the black plastic part on which the on/off switch sits.

The brown cable sits next to N.C. and the blue cable next to N.O. The grey cable is attached underneath this black plastic part.

From this, is anybody able to tell me which terminals I should be attached the slate, blue and brown cables please?

The photo of the converted 706 on the BritishTelephones web site does not appear to have these 3 extra cables and I can't really make sense of the diagram.

Thanks again for all the help!
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Old 11th Mar 2018, 6:35 pm   #7
Dave Moll
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Default Re: 706 Phone Conversion Help

Having dug a similar switch out of my component store, I can confirm that slate is common, brown is closed in the "off" position and blue is closed in the "on" position, so following my wiring outlined earlier:

slate of switch to T16
blue of switch to T13
orange of ringer also to T13
and park brown of switch on (say) T14 (spare)
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Old 11th Mar 2018, 7:12 pm   #8
absolutelynice
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Default Re: 706 Phone Conversion Help

Thanks Dave!
I just tested it out and there was no ring though unfortunately.

Do you know where should the second orange cable from the ringer should go please?
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Old 11th Mar 2018, 7:19 pm   #9
TonyDuell
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Default Re: 706 Phone Conversion Help

Terminal T4, that is the left hand end of the added resistor in your photo.
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Old 11th Mar 2018, 7:34 pm   #10
absolutelynice
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Default Re: 706 Phone Conversion Help

Sorted! For some reason it was under T16.

Last thing sorry, the ringer works when the on/off button is pressed down at the off side (photo attached). Is that right?

Thanks for all the help Dave, really appreciate it!
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Old 11th Mar 2018, 9:52 pm   #11
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Default Re: 706 Phone Conversion Help

If the "on" and "off" legends are the wrong way around, then swap over the brown and blue wires to the switch, leaving the slate grey wire wherever it is.
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Old 11th Mar 2018, 10:03 pm   #12
absolutelynice
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Default Re: 706 Phone Conversion Help

Quote:
Originally Posted by TonyDuell View Post
Terminal T4, that is the left hand end of the added resistor in your photo.
Sorry Tony, I thanked Dave in my last reply but I was meant to thank yourself

Quote:
Originally Posted by julie_m View Post
If the "on" and "off" legends are the wrong way around, then swap over the brown and blue wires to the switch, leaving the slate grey wire wherever it is.
Thanks Julie, I'll give this a try tomorrow
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Old 18th Mar 2018, 9:05 pm   #13
absolutelynice
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Default Re: 706 Phone Conversion Help

Thanks so much for everyones help, the phone is now fully functioning!

I just thought I'd post a picture of the wiring incase anybody else has the trouble in future.
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Old 18th Mar 2018, 9:11 pm   #14
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Default Re: 706 Phone Conversion Help

Good to know you have it sorted.
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