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Old 22nd Apr 2012, 2:37 pm   #21
Twin Pin
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Default Re: Trouble with a 706 faint dial tone.

I would say have a look at the back of the dial and make sure the off-normal contacts are working and properly separating when the dial returns to the home position. Sometimes they don't separate properly which can cause quiet receiver or no dial tone. I have come across this problem a couple of times with my collection and it is easily remedied by adjusting the little leg that pushes the contacts.
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Old 29th Apr 2012, 12:48 pm   #22
mike_newcomb
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Default Re: Trouble with a 706 faint dial tone.

Hi Dave, to clarify my experience.

The phone socket on the broadband splitter/filter was physically *missing* the metal pins for contacts 3 and 4.

Although pin 4 is not used (but sometimes wired for tidyness), pin 3 is necessary for handsets with a UK ringing circuit. Thus if no pin 3, the handset can call out and receive calls perfectly (as pins 2 and 5 are used) but it will not ring.

This was one of those nightmare faults, that at every stage of the investigation, something wrong was found, but when corrected, the fault remained. Causing much tearing out of hair!

After every section of the circuit had been metered and shown to now be correct, the filters were dismantled and the one being used by the phone was found to be missing the pins. This is not something one would generally visually check, but since then I have checked all filters for this deficiency.
Regards - Mike
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Old 29th Apr 2012, 5:26 pm   #23
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Default Re: Trouble with a 706 faint dial tone.

Interesting, Mike. See also here: http://www.adslnation.com/support/filters.php

Apparently, some utter rubbish about.
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Old 29th Apr 2012, 6:59 pm   #24
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Default Re: Trouble with a 706 faint dial tone.

Well the microfilters and phones sold in the high street are from the far east and perhaps they do not support 3 wires.
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Old 4th Sep 2012, 9:14 pm   #25
bubasparks
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Default Re: Trouble with a 706 faint dial tone.

I had exactly the same problem with faint reception with my 706. It turns out if you push the PCB towards the dial, Hey Presto! I could not find any cracks or dry joints so ended up securing the board with a little bias forward.
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Old 5th Sep 2012, 8:44 am   #26
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Default Re: Trouble with a 706 faint dial tone.

Are you talking about the main PCB which is screwed to the base, or the regulator which plugs into it?
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Old 5th Sep 2012, 10:11 am   #27
Nickthedentist
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Default Re: Trouble with a 706 faint dial tone.

Quote:
Originally Posted by bubasparks View Post
I had exactly the same problem with faint reception with my 706. It turns out if you push the PCB towards the dial, Hey Presto! I could not find any cracks or dry joints so ended up securing the board with a little bias forward.
Cracked tracks on the main PCB are very common after a PCB-built 706 is dropped, and repairs were often made by the GPO using insulated copper wire on the track side of the board. Obviously, the hard-wired style is more robust in this respect.

And the small regulator sub-PCB can sometimes make intermittent contact with the main PCB, as Graham's implied. Cleaning and retensioning the contacts is the solution here.

Nick.
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