GPO 706 CB diagram ?

[FABphones]

Next on the workbench is this 1961 GPO 706 Mark I in fairly poor condition - grubby, dial hanging off, dial surround missing, damaged and taped handset cord, and loose case.

Purchased as the base is marked 706 CB.

Returning it back to CB, the dial is now removed - but need a 706 CB wiring diagram. Have searched unsuccessfully.

Can anyone help or take a photo of the inside of theirs so I can wire this one up as was?

Thanks.
 

[FABphones]

This one maybe?

http://www.classicrotaryphones.com/forum/index.php?topic=25547

[dsk]

I guess that the circuit is right, but pretty typical is that the ringercapacitor is missing, (and you may use smaller than 1.8uf as replacement)  The 0.9 uF capacitor is in use in another part of the circuit. The other common fault is that the regulator bridge may cause trouble, if it is the plug in circuit board it is another position to plug it in to omit thet part of teh circuit for long loops.

[tubaman]

I guess that the circuit is right, but pretty typical is that the ringercapacitor is missing, (and you may use smaller than 1.8uf as replacement)  The 0.9 uF capacitor is in use in another part of the circuit. The other common fault is that the regulator bridge may cause trouble, if it is the plug in circuit board it is another position to plug it in to omit thet part of teh circuit for long loops.

The 0.9uf capacitor you can see on the phone is actually a dual 0.9/1.8uF unit that is common to this age of GPO phones. That is why it is marked C1A and C1B on the diagram as it is two capacitors on one case.

[tubaman]

@FABphones, hopefully the attached pamphlet will answer your wiring questions (and be of general interest).
 

[FABphones]

...hopefully the attached pamphlet will answer your wiring questions (and be of general interest).

Very much so! Thank you 👍.

——

Images below show the phone body removed from base, and front/rear of Dummy Dial #6 (purchased separately) as originally fitted to the Mark I CB.

Directions to help anyone who may need to fit one of these...

To replace the dummy dial work from inside of the phone body.

- Gently slide one of the metal arms into position (metal arm goes inside, plastic remains outside the phone body).
- To move the second arm into position gently turn and slide the dummy dial so this arm also slides under and into position.

The third arm is the tricky one.
- I used a small lifting tool to carefully lift each arm as necessary until the dummy dial could be moved slightly too far over to give clearance for the third arm, allowing it to slot into place. The cutouts as shown in the image below help give extra clearance. Once all three arms are in position carefully adjust the complete dummy dial until it sits correctly down on the body. You can see when it sits properly as there are no gaps between dummy dial and phone body.

[tubaman]

Looks like the bracket should twist off from the blank - doesn't it do that?

[FABphones]

Looks like the bracket should twist off from the blank - doesn't it do that?

I was thinking so, tried but to no avail. I thought the centre piece should twist and come out releasing the metal sections but mine would not move. I didn't want to damage it so used the above method. Fiddly, but it worked. I have since found another #6 without the metal parts so they definitely do come away.

 

—-

The phone is cleaned up and reverted back to original CB.

None of the Opals I have fit, their diameter is too large. Same issue with the Dial Cards.

Untested as it needs a replacement handset cord. Went through my cords and I have many variations, but not this one. So until an original cord can be found this phone will come off the workbench and onto display as I need the room to work on the next.

A cord (and hopefully Opal) will come along, it is worth the wait to get it right.   

Thanks everyone for the help.