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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment

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Old 6th Aug 2007, 10:50 am   #1
BMXXKSD
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Default Trim phone. Can't break dial tone.

I've also got a problem with a Trimphone (model 2/722). The dialling tone continues after I start dialling and so it' not possible to dial out (everything else works fine). i've changed the little black box that sits under the handset cradle but no luck. Any ideas?

Thanks
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Old 6th Aug 2007, 11:01 pm   #2
Station X
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Default Re: Trim phone. Can't break dial tone.

The first thing I'd check is whether your telephone line supports Loop Disconnect (LD) dialling also known as pulse dialling. It's possible it only supports MF4 (tone dialling).

Do other types of dial telephone work on your line?

Disconnect the trimphone from the line and connect an analogue multimeter on ohms range across its line terminals. Having obtained a steady reading dial the digit "0". You should see the needle flickering as the phone goes open circuit with each dial pulse. This indicates that the phone itself is working correctly as far as dialling is concerned.
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Old 7th Aug 2007, 11:07 pm   #3
BMXXKSD
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Unhappy Re: Trim phone. Can't break dial tone.

Thanks Station X

I do have other dial phones (300 series) and all of these can dial out without any problem. Someone has suggeted there may be a short in the ringing circuit but I don't know how to test this.

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Old 8th Aug 2007, 7:16 am   #4
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Default Re: Trim phone. Can't break dial tone.

Quote:
(everything else works fine).
So the phone warbles on incoming calls, you can answer the phone, hold a conversation and clear down without blocking the line to further incoming calls, or preventing other phones from making calls?

If you can't dial, then either the dial isn't generating dial pulses (open circuits to line) or something is short-circuiting the the dial contacts.

What was the result of the test I suggested? When the dial is rotated from its rest position almost a short-circuit should be presented to line. Each dial pulse should be an open circuit to line. If you restrain the dial so that it returns slowly to its rest position you should clearly see each dial pulse register on the meter.

Try disconnecting the ringer unit amd capacitor to see if this makes any difference.
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Old 8th Aug 2007, 9:12 am   #5
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Default Re: Trim phone. Can't break dial tone.

I assume you've checked out the info here:-

http://web.ukonline.co.uk/freshwater/t722.htm
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Old 8th Aug 2007, 11:01 pm   #6
BMXXKSD
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Thumbs up Re: Trim phone. Can't break dial tone.

Many thanks, Graham.

Your comments about the dial contacts reminded me that I had another dial spring and contact set. When I eventually found it and fitted it to the Trimphone the problem did not recur.

Thanks for your immediate responses and your patience.

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