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-   -   Problem with dial 24c dial making clicking noises on 232 telephone (https://www.vintage-radio.net/forum/showthread.php?t=170527)

john777 28th Aug 2020 3:09 pm

Problem with dial 24c dial making clicking noises on 232 telephone
 
Hello
I have a 232 bakelite phone with a type 24c dial on.
It is working correctly, I can dial out and dial in and sound quality pretty good.
The only problem is when I dial out I can hear a clicking sound which is not nice on the ear.
Does anyone know what could be causing this and whether it can be cured.
I know later phones were fitted with a rectifier to stop this but is it possible to fit this on a 232?
Many thanks for reading

Dr-of-style 28th Aug 2020 4:40 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
I don't know the 232 phone, but it is all about space... for the double diode pop reducer.
if there is room. across the rec screws. or inside the phone?
or maybe the dial contacts need attention? or a different switch config?

pip5678 28th Aug 2020 4:45 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
It could be the dial contacts that need a clean, there are dial off normal contacts (these make when the dial is off normal) which short out the transmission components.

TonyDuell 28th Aug 2020 4:46 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
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.

dagskarlsen 28th Aug 2020 4:47 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
2 Attachment(s)
The dial has some shorting contacts shorting out the circuit, so you should only hear a click when the dial is moved out of rest position, and one when it is coming to the rest position. The diode bridge may fit in the phone across the wires going to the receiver.

The diode bridge will fit between the 2 terminals inside the ring.

dsk

Pellseinydd 28th Aug 2020 5:43 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
2 Attachment(s)
Quote:

Originally Posted by TonyDuell (Post 1284007)
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!

Pellseinydd 28th Aug 2020 5:52 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
Quote:

Originally Posted by dagskarlsen (Post 1284008)
The dial has some shorting contacts shorting out the circuit, so you should only hear a click when the dial is moved out of rest position, and one when it is coming to the rest position. The diode bridge may fit in the phone across the wires going to the receiver.

The diode bridge will fit between the 2 terminals inside the ring.

dsk

Receiver is across Terminals 5 and 8. Not T 4 and T 5

dagskarlsen 28th Aug 2020 7:57 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
Quote:

Originally Posted by Pellseinydd (Post 1284030)
Quote:

Originally Posted by dagskarlsen (Post 1284008)
The dial has some shorting contacts shorting out the circuit, so you should only hear a click when the dial is moved out of rest position, and one when it is coming to the rest position. The diode bridge may fit in the phone across the wires going to the receiver.

The diode bridge will fit between the 2 terminals inside the ring.

dsk

Receiver is across Terminals 5 and 8. Not T 4 and T 5

On mine (picture with yellow ring) and the yellowish diagram is from mine, has the receiver on terminals 5 and 6 so it has obviously been at least 2 versions.

dsk

Dave Moll 28th Aug 2020 9:04 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
Yes, the N diagram confirms that T6 and T8 were reversed on earlier versions such that the receiver was connected between T5 and T6 - as shown in the paster diagram posted by DSK earlier.

john777 11th Sep 2020 1:27 pm

Re: Problem with dial 24c dial making clicking noises on 232 telephone
 
hello
Basically cleaned all the points on the dial, did not have any alcohol so used meths.
There was an immediate improvement. So looks like job done
Many thanks to all those people who took the trouble to reply


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