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Old 8th Jun 2012, 8:32 pm   #1
Gavcr999
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Default Push Button 766 Trimphone Dialling Problem

Hi,

I've just wired up a GPO766 pushbutton Trimphone for plug and socket. It works except for that you can't dial out. When you press any of the pushbuttons the dialtone cuts out when it is pressed but then returns a second or so later.

Any help or advice as to what may be causing the problem would be very much appreciated!

Many thanks,
Gavin
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Old 8th Jun 2012, 9:45 pm   #2
bobbyball
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Default Re: Push Button 766 Trimphone Dialling Problem

Possibly an obvious question but does your line actually support "pulse" dialling?

Robert
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Old 8th Jun 2012, 9:50 pm   #3
kernowcam
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Default Re: Push Button 766 Trimphone Dialling Problem

Battery?
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Old 8th Jun 2012, 10:06 pm   #4
Gavcr999
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Default Re: Push Button 766 Trimphone Dialling Problem

Quote:
Originally Posted by bobbyball View Post
Possibly an obvious question but does your line actually support "pulse" dialling?

Robert
Hi, yes I have several GPO 700, 300 and 200 series phones which all work fine. This is the first push button pulse dialling phone I've had though.
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Old 8th Jun 2012, 10:45 pm   #5
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Default Re: Push Button 766 Trimphone Dialling Problem

I have one in pieces at the moment. Dial unit doesn't take a battery like the earlier units. It's a very complicated circuit, no doubt very advanced for it's time. Check the contacts under the buttons and for bad connections. There are 6 wires connecting mine to the main PCB, are all these connected OK?

Robert
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Old 8th Jun 2012, 10:57 pm   #6
julie_m
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Default Re: Push Button 766 Trimphone Dialling Problem

Try an analogue meter (on 50V DC range) across the line. The needle should flick up briefly in sympathy with the dialling pulses, if it is sending them.
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Old 8th Jun 2012, 10:59 pm   #7
Gavcr999
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Default Re: Push Button 766 Trimphone Dialling Problem

I seem to have just 5 on mine as below:

Brown - T3
Pink - T10
Orange - T8
Blue - T2
Grey - T1

This seems to correspond ok to the terminal numbers printed on the keypad PCB. But there are only these 5 connections.
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Old 8th Jun 2012, 11:32 pm   #8
bobbyball
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Default Re: Push Button 766 Trimphone Dialling Problem

There are several versions obviously! You could try a conventional dial "borrowed" from one of your 700 series phones to check the rest of the phone is working.

Robert
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Old 12th Jun 2012, 11:24 pm   #9
mkmagna
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Default Re: Push Button 766 Trimphone Dialling Problem

I have a similar problem with a 756 phone so I'll be watching this thread with interest.
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Old 13th Jun 2012, 8:04 pm   #10
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Default Re: Push Button 766 Trimphone Dialling Problem

Are we sure this is pulse dialling? I have (had?) some DTMF-only Trimphones somewhere, so they do exist. They were no doubt designed as PBX extensions as they predate the widespread introduction of DTMF dialling from subscribers' lines. They do work at home, but you have to hold down each button a little longer than you might normally to ensure that the exchange recognises the tone; quick, "staccato" dialling doesn't work reliably.

I also have a few of the DTMF 746-style phones of various vintages and models. At least one wouldn't dial out, and I'm afraid it was the DTMF generator chip (a Ferranti one, ISTR) which had failed. Impossible to obtain except by cannibalising another phone.


N.

Last edited by Nickthedentist; 13th Jun 2012 at 8:10 pm.
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Old 13th Jun 2012, 9:21 pm   #11
Dave Moll
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Default Re: Push Button 766 Trimphone Dialling Problem

Quote:
Originally Posted by Nickthedentist View Post
Are we sure this is pulse dialling?
If it is a 766, it is pulse dialling.
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Old 13th Jun 2012, 9:44 pm   #12
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Default Re: Push Button 766 Trimphone Dialling Problem

Thanks for the clarification, Dave.
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