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Old 11th Jun 2019, 5:01 am   #41
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 3,261
Default Re: GPO planset with external extensions

If everything is correct the diode will work immediately. It does not need to warm up.

The silver stripe on the diode is indeed the cathode, and as the N diagram shows it goes to terminal 5. The diode is normally reverse-biased.
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Old 11th Jun 2019, 10:25 pm   #42
Shmason
Triode
 
Join Date: Jun 2019
Location: Leek, Staffordshire, UK.
Posts: 21
Default Re: GPO planset with external extensions

Hi Tony et al,

You will be pleased to know this will probably be one of my final messages on the subject, for a while anyway!

In addition to working full time I am supposed to be doing some consultancy work in the evenings which is falling behind as I am trying to fix this! I am a perfectionist at heart and want everything to be correct, however, aside from the buzzer not working when you call the home phone with the main switched as extn to exch, all other functions are fine. I did some final testing with my partner tonight and found that we could:

Call the house from a mobile, answer on main
Put call on hold and speak to extension
Put call through to extension
'buzz' the main to transfer the call back
Make and receive internal calls from extension to main and vice versa.

One final thought is that my friend directed me to this link:

https://www.britishtelephones.com/plans625.htm

The part that interested me was:

RECORDS
When the line is tested through to an external extension the current through the test-desk meter will not be sufficient to operate relay A, thus relay B will remain in series with the line. The following note should be made in the remarks column on the fault card:- "The line resistance to an external extension will be increased by 400 ohms unless a short circuit is applied between terminals 4 and 5 of the Converter, Ringing, No. 9A"

I wonder if this is a similar issue to what I have. I put a meter across the ring converter coils again. Without the diode I'm getting approx 11v AC when calling from a mobile and only 4v DC with the diode fitted in parallel. A friend advises me this is not a 'true' reading as multimeters work on 50hz signals but this may be a sign that not enough current is getting to the ring converter relay?

I have also been getting help from somebody via DM and we have established the wiring in the plinth does not tie back to the N diagram. Sadly I just do not have time at present to rewire it all and as it is working so near perfectly I'm pretty darn happy. Just if you can think of a little 'oh check this, is there a resistor here etc' that would be great, otherwise thank you so so much for taking all this time and trouble.

Jason
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Old 12th Jun 2019, 4:59 am   #43
TonyDuell
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Location: Biggin Hill, London, UK.
Posts: 3,261
Default Re: GPO planset with external extensions

Do you have any other telephones on the same BT line?
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Old 12th Jun 2019, 6:49 am   #44
Shmason
Triode
 
Join Date: Jun 2019
Location: Leek, Staffordshire, UK.
Posts: 21
Default Re: GPO planset with external extensions

Yes. And I have tried unplugging every single one to see if it made a difference!
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