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help needed: field telephone type L (picture heavy)

 
meddy
(@meddy)
Trusted Member

ok so i dug around in the lock up for my field telephones and found three so far before the cold drove us back home

so we managed to dig up 2X field telephone type L mk1/1 and a dcell powered newer one that one works fine, now its the others i need help with i have tried running the tests on the instructions i can hear the generator crackling over the lines but the bells aren't ringing. i tried 3v in the battery box to try and get the mics running but noting happened or it was to quiet to hear i don't know.

no does anyone have any knolage on thes kinds of phones. i went around with me trusty multy meter the cables are conducting fine the big thing in the bell curckit dosent register a flow well that about it realy
heres some images

would love to get these working for my local sites foray into WW2 themed event scermish weekend in April even if sigh complacently rewiring it helps ill do it.

the only googlefu that helped was a old pc gaming buddy sent me this link to the mark F type

... 9-STV3-P23

thanks for looking any help advice or instructions would be greatly appreciated and i will shower you in internet cookies and spiders because they need love to ;)

meddy

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Topic starter Posted : 16/03/2013 3:44 am
McVickers
(@mcvickers)
Famed Member

now does anyone have any knolage on thes kinds of phones.

Yes, lots!

Operation
Ensure that the little button-looking-thing labelled 'CB' is pushed down on both phones. You'll be using them peer-to-peer, to the Central Battery calling switch is not required.

Faults
The most common fault you'll find is that the handset cable is broken, and nearly always on the Mic' side (sods law!) which is the two wires running to the handset plug on the outsides (both marked 'M', one should be colour coded yellow, and the other colour coded blue). Don't bother trying to buzz out the mic', and it's a carbon mic', and not a coil mic'.

The mic' itself, being a capsule packed full of carbon granules, usually don't work after sitting about for 70 odd years and need to be struck/hit/shaken hard to loosen and free-up the granules again. This method sounds a harsh thing to do, but that's the only suitable way to loosen them back up. Don't do what most do and hit the handset on a table, this could damage the Bakelite casing and will help to demagnetise the magnets in the earpiece. Remove the mouthpiece cover (rotate anti-clockwise 40 degrees, you may need to push in some little spring tabs before it will move - depending on your model of handset) and pull out the mic' capsule (it's a push-fit, so just lift it out) and give it a shake, listen carefully and if you can hear a light 'chaffing' sound of the loose granules, then the mic' is fine. If you can't hear the granules moving, then give it a knock on its side. While the capsule is out, give the mic' leads a buzz-out.

If you do feel the need to poke around and take the earpiece apart, remove the membrane disc by sliding it off of the coil magnets sideways, and slide it back on again for reassembly - don't lift it off or drop it back in place.

The bells not ringing on another phone connected to it could well be the dynamo's switch contacts (it connects itself to the line automatically when ever you turn the handle) are dirty and need cleaning. A piece of clean printer paper with a little isopropyl alcohol or similar contact cleaner (Not WD40! Ever!) passed between closed contacts should clean them sufficiently. Also, measure across the L1 and L2 line terminals when cranking the dynamo, you should see about 90Vac.

A Proud Member Of 'Team Spleen!' who play mainly at Gunman Airsoft, Tuddenham, Suffolk.

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Posted : 17/03/2013 1:30 am
meddy
(@meddy)
Trusted Member

Yey somethig to do on padys day after first aid traing day :)

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Topic starter Posted : 17/03/2013 2:38 am
meddy
(@meddy)
Trusted Member

Hmmm so would a flat tourch bat work powering it? Think they are 4.5 or would a large 8.4 airsoft bat work got loads of thoes spair

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Topic starter Posted : 17/03/2013 5:07 pm
McVickers
(@mcvickers)
Famed Member

They're designed to work off of 3V. Two 'D' cell batteries in an appropriate "side-by-side" holder fits lovely into the battery compartment (I can take pictures of what I do to mine if you'd like to see). They don't need a lot of current to operate and should even work fine off of two 'AA' cell batteries.

A Proud Member Of 'Team Spleen!' who play mainly at Gunman Airsoft, Tuddenham, Suffolk.

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Posted : 17/03/2013 7:21 pm
meddy
(@meddy)
Trusted Member

hmmm the cables insulation is rather perished inside shuld i replace it with moden wire? or just tape it up

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Topic starter Posted : 18/03/2013 2:57 pm
meddy
(@meddy)
Trusted Member

Well thats one of them wires all re insulated :) the mics are working now and the bells are sort of working but i havent cleaned the contacts yet (no cleaning fluid >o<

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Topic starter Posted : 18/03/2013 10:32 pm
McVickers
(@mcvickers)
Famed Member

It's an interesting thing, to point out (especially if anyone else is looking to aquire field telephones) that out of all of my phones, the ones which look the clean and tidiest, are the ones which don't work because all of the natural rubber wire insulation has dried out and cracked off - where as the scruffy rusty ones work the best and the insulated wires still have some flex in them!

Can't win, can we, eh?

A Proud Member Of 'Team Spleen!' who play mainly at Gunman Airsoft, Tuddenham, Suffolk.

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Posted : 20/03/2013 12:58 am
meddy
(@meddy)
Trusted Member

hehe bit like the airsoft guns I get grubby they are the better they work (see: 4 year old hire gun ak shot billions of bbs all it needed was a spring ^^)

if I get time tomorrow I should clean up the external contacts on the geni don’t know if I should dismantle it though it looks like a sealed unit so shouldn’t be rusted inside should it?

the other one looks in better condison on the cables but ill still give it a good look over.

also re did the cables on the handsets as one of them was frayed inside at the join and the other was just a bit loose

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Topic starter Posted : 20/03/2013 2:54 am
McVickers
(@mcvickers)
Famed Member

hehe bit like the airsoft guns I get grubby they are the better they work (see: 4 year old hire gun ak shot billions of bbs all it needed was a spring ^^)

if I get time tomorrow I should clean up the external contacts on the geni don’t know if I should dismantle it though it looks like a sealed unit so shouldn’t be rusted inside should it?

No, shouldn't be, they're pretty simple bits of kit and I've never had one go wrong. The simplist way (and actually an official Brit army way) of testing the output of the dynamo is to lick your finger and thumb, and hold both terminals at the same time with your wetted fingers, and use your other hand to crank over the dynamo a few spins. If you feel an electrical jolt, then it's working!

Either that, or measure the AC voltage (with your multimeter) across the two terminals when you crank the dynamo, it should be about 90Vac, but a reading as low as 60Vac is still fine...

A Proud Member Of 'Team Spleen!' who play mainly at Gunman Airsoft, Tuddenham, Suffolk.

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Posted : 20/03/2013 5:26 pm
meddy
(@meddy)
Trusted Member

ah yes forgot to mention the earpieces don't have that type of diaphragm there crinkled circles made of blue plastic with a little nut in the middle. ill take a pic when i get them out next

I don't know maybe the bells electro magnets need ....something doing to them

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Topic starter Posted : 20/03/2013 5:55 pm
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