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Old 29th Apr 2019, 12:31 pm   #1
adamcable
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Default 312L Conversion

Hi all,

I'm desperately trying to help a friend get her 312L working again.

I work in IT but am very naive in this world, so looking for help.

I've bought a conversion kit, and wired it up per the instructions. The handset wiring was cut so just testing the base unit for now.

When I plug it into the phone socket, it automatically picks up/shows as engaged when you phone it, even whilst holding down the receiver buttons. I can hear the pulse tones when using the dial which only sound when I let go of the receiver buttons.

I'd love to hear the magical ringing bells when the phone is called - but how do I stop it from always being engaged? Do I need to fix the handset before this will happen? I've added some pictures in case it helps!

Many thanks,
Adam, Ipswich
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Old 29th Apr 2019, 12:47 pm   #2
pip5678
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Default Re: 312L Conversion

There are several version of 300 series telephones, conversion wiring differs between them. Are you wiring for a 312?
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Old 29th Apr 2019, 12:54 pm   #3
adamcable
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Default Re: 312L Conversion

Thanks for your message, pip5678.

I've followed all the instructions for wiring:
Link terminals 1-2-3-9 together
White line T1
Red line T8
Blue line T11
Green line T7 (redundant)

Strap T1-T2
205 Rectifier T5-T6
Strap T8-T9
3.3k resistor T11-T12

Adam
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Old 29th Apr 2019, 1:05 pm   #4
Dave Moll
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Default Re: 312L Conversion

There are instructions for wiring for plug and socket here.

A full wiring diagram for the 312 can be found here. Note, however, that the difference belween a 312 and a 322 is that the former is wired for a shared line, so 322 wiring may be more appropriate.
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Old 29th Apr 2019, 1:15 pm   #5
adamcable
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Default Re: 312L Conversion

Thanks Dave. I've now wired it up as per http://www.samhallas.co.uk/repositor.../0000/N432.pdf and the phone now rings, but doesn't answer when I release the two receiver buttons.

I guess I now need to fix the receiver and attach it to allow that to happen.

Adam
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Old 29th Apr 2019, 1:48 pm   #6
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Default Re: 312L Conversion

Adam, haven't got time at the minute to do a full diagram check but try without T8-T9, lack of handset shouldn't make a difference for what you're trying, Pip
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Old 29th Apr 2019, 1:58 pm   #7
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Default Re: 312L Conversion

Quote:
Originally Posted by adamcable View Post
...the phone now rings, but doesn't answer when I release the two receiver buttons.

I guess I now need to fix the receiver and attach it to allow that to happen.

Adam
Do I infer from the above that you don't have the handset wired in? If this is the case, that is certainly the source of not making a loop (going "off-hook"). The transmitter (microphone) in the handset is an integral part of the loop.

If it is just the receiver (earpiece) that is not connected, the loop should be made when the handset cradle buttons are released - unless the transmitter inset is faulty.
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Old 29th Apr 2019, 2:00 pm   #8
adamcable
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Default Re: 312L Conversion

That's correct - someone decided to take a pair of scissors to the lovely curly cable...thanks for this info, really appreciated!
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Old 29th Apr 2019, 5:32 pm   #9
pip5678
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Default Re: 312L Conversion

Quote:
Originally Posted by Dave Moll View Post
Quote:
Originally Posted by adamcable View Post
...the phone now rings, but doesn't answer when I release the two receiver buttons.

I guess I now need to fix the receiver and attach it to allow that to happen.

Adam
Do I infer from the above that you don't have the handset wired in? If this is the case, that is certainly the source of not making a loop (going "off-hook"). The transmitter (microphone) in the handset is an integral part of the loop.

If it is just the receiver (earpiece) that is not connected, the loop should be made when the handset cradle buttons are released - unless the transmitter inset is faulty.
If you read Adam's original post it looks like the instrument is putting a loop on the line. This is likely because there was a link from T8 to T9 and terminals 1,2,3 and 9 are also linked. On N412 diagram this will short the line regardless of any handset connections. N432 is the wrong diagram!

Last edited by pip5678; 29th Apr 2019 at 5:48 pm.
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Old 29th Apr 2019, 5:53 pm   #10
adamcable
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Default Re: 312L Conversion

Thanks all.

Two final questions if I may.
1 - how do I disconnect the middle (red) cable from the handset (picture attached)?
2 - how do I say thanks to you all for the wonderful support you've given?

Thanks,
Adam
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Old 29th Apr 2019, 7:00 pm   #11
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Default Re: 312L Conversion

Box spanner or a pair of pliers it just unscrews, do let us all know if you get the phone working, Pip
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Old 29th Apr 2019, 10:37 pm   #12
Dave Moll
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Default Re: 312L Conversion

Quote:
Originally Posted by pip5678 View Post
Quote:
Originally Posted by adamcable View Post
...the phone now rings, but doesn't answer when I release the two receiver buttons.

I guess I now need to fix the receiver and attach it to allow that to happen.

Adam
If you read Adam's original post it looks like the instrument is putting a loop on the line.
I interpret "doesn't answer" as meaning the bell continues to ring. In the original post (which I did read), Adam was not getting ringing at all as there was a permanent loop. This was not the case in the post to which I responded.
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Old 30th Apr 2019, 8:01 am   #13
pip5678
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Default Re: 312L Conversion

Apologies Dave Moll, some of the posts crossed and Adam did some work between them, this changing the nature of his issue, regards, Pip
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Old 30th Apr 2019, 9:59 am   #14
adamcable
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Default Re: 312L Conversion

Quote:
Originally Posted by pip5678 View Post
Apologies Dave Moll, some of the posts crossed and Adam did some work between them, this changing the nature of his issue, regards, Pip
Apologies, as I'm new to this forum, I think my posts have to be approved before they are posted, which means that the thread is a little disjointed!

Adam
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Old 3rd May 2019, 4:50 pm   #15
adamcable
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Default Re: 312L Conversion

Hi All!

I'm now really close. Have wired everything up!

The phone rings, it answers, when you speak, people can hear you, it dials out, but you can't hear anyone - the receiver is extremely temperamental.

I can only get it to work by holding the microphone in a specific place (after wiggling around for a while and waiting to hear a dial-tone), but as soon as I let go/screw the cover in, it stops.

I have tried two handset cords but both have the same issue.

Any ideas?

Thanks,
Adam
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Old 3rd May 2019, 5:13 pm   #16
pip5678
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Default Re: 312L Conversion

Confusing! As mentioned in #7 the transmitter is part of the loop required to get dial tone or trip the ringing so you may still have a wiring issue. Diagram N412 refers to the 312 not N432 which is for the 332 telephone and is configured differently. There is a springset within the dial that short out the receiver when the dial is off normal to prevent pulsing in the receiver, there could be an issue here and there is a diaphragm in the receiver isn't there?
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Old 3rd May 2019, 7:22 pm   #17
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Default Re: 312L Conversion

Might be a poor connection within the transmitter (microphone) part of the handset. Note how the horseshoe spring and the central spigot bear on the back of the transmitter. They are brought into contact when the mouthpiece is tightened. In fact looking at your photo I'm not sure that the spring has the correct profile.

Alan
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Old 3rd May 2019, 8:22 pm   #18
pip5678
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Default Re: 312L Conversion

Agree with Alan the pips on the 'horseshoe spring' ends should contact the back of the transmitter insert, they easily bend!
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Old 3rd May 2019, 9:29 pm   #19
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Default Re: 312L Conversion

You could carefully splay the legs of the centre contact pin too.
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Old 5th May 2019, 5:34 pm   #20
adamcable
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Default Re: 312L Conversion

All is now working. Someone had undone a screw behind the diaphragm which was causing it to struggle to vibrate. Sometimes the simplest fixes are the best!

Thank to you all for your kind input - it really is appreciated.

Adam
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