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Old 28th Aug 2020, 5:43 pm   #6
Join Date: Jul 2007
Location: Flintshire, UK.
Posts: 614
Default Re: Problem with dial 24c dial making clicking noises on 232 telephone

Originally Posted by TonyDuell View Post
I am not sure what the Dial 24C is, but I am assuming it's the same electrically as the dial normally used in the Telephone 232.

In which case try cleaning the off-normal contacts (the ones that close when the dial turned from the rest position). One pair of contacts short-circuits the receive to prevent said clicks.

DO NOT use abrasive, you will ruin the contacts. I normally cut a thin strip of paper, soak it in isopropyl alcohol (propan-2-ol), put it in the gap between the contacts, turn the dial so the contacts close, and pull the paper out. There's then a dark streak on the paper...

Repeat a few times and see if things improve.
The 'Dial 24C' is electrically the same as the Dial No 10. It was produced by Automatic Telephone & Electric and fitted to many versions of their 200/300 style telephones. Their catalogue mentions that they were interchangeable.

The 24C is/was said never to have been adopted by the GPO . I've never come across reference to it in any GPO Documentation. However I have a Tele 16 that had been converted by the GPO for automatic working but had never been used when I bought it many years ago - it still had two screws wrapped in brown paper tied to the terminal block in good old GPO fashion!. It has a Dial 24C fitted and that has 'GPO' stamped in yellow paint on the rear - the dial that is, not the phone!

The circuit should be that of a Tele 232 even if it is an AT&E version see GPO circuit diagram N332 for the Tele 232..

With a test meter set to ohms, you should get a complete short between Terminal 4 and Terminal 7, and between Terminal 6 and 7 when the dial is held 'off normal' . That is after cleaning the contacts as suggested. That should show which of the contacts is the problem. Could be a faulty dial cord - not unknown!
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Last edited by Pellseinydd; 28th Aug 2020 at 5:50 pm.
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