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Old 28th Dec 2017, 5:05 pm   #41
russell_w_b
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Default Re: GEC 1000 phone not working properly?

It's a Handset No:1 that takes a Mic, Inset, No:13, same as on an Australian Type 400 instrument. The Handset No:3, which also used to use an inset 13 mic, incidentally, years ago, is a lightweight plastic (diakon on older teles) handset, not the heavy Bakelite thing on the GEC1000. The shapes are similar and both handsets use a rocking armature receiver.

The Type 13 inset mics are common enough and there'll be plenty kicking around. http://www.britishtelephones.com/hands1.htm
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Old 28th Dec 2017, 6:35 pm   #42
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Default Re: GEC 1000 phone not working properly?

Quote:
off hook 4.2v
That seem rather low. Usually about 10-15 volts when off hook.
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Old 28th Dec 2017, 6:47 pm   #43
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Default Re: GEC 1000 phone not working properly?

Depends on distance to exchange I guess, Tim: volt drop on line resistance and all that, although there will be some regulation. I live 6.8km from our exchange and measured the voltages in post #25.

There may even be a H/R line fault somewhere!
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Old 28th Dec 2017, 7:02 pm   #44
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Default Re: GEC 1000 phone not working properly?

The BT SIN351 doesn't give an 'off-hook' voltage but gives the following useful data: 'The d.c. current provided at the customer side of the NTP will be up to 42 mA at 12.5 V, up to 33.5 mA at 10 V, and will be not less than 25 mA at 9 V.'

So with a lower off-hook voltage than 9V you're pushing it a bit.
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Old 28th Dec 2017, 10:13 pm   #45
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Default Re: GEC 1000 phone not working properly?

Random suggestion. Is the polarity of the line the same at the two premises? It shouldn't of course make a difference but there may be some bizarre fault on the telephone which can't cope with incorrect line polarity.
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Old 28th Dec 2017, 10:26 pm   #46
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Default Re: GEC 1000 phone not working properly?

The line polarity sometimes changes upon different call conditions - or used to. It ought make no difference to the telephone. The only way polarity will make a difference is if wires 2 and 5 are reversed with relation to the bell / anti-tinkle wire, i.e: at the socket-side of the master box.

But IF the telephone had a wire touching the chassis within, and IF the chassis happened to be touching earth...
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Old 30th Dec 2017, 5:31 pm   #47
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Default Re: GEC 1000 phone not working properly?

I've had to dig mine out now...

The pic shows the Mic, Inset No: 13 with spring-ring around the 'flying saucer' and you will see the bent-back protrusion that engages with the notch in the side of the mouthpiece cup. The connections are as shown, but the mic pin that connects to the rear of the inset is one I cut down from a scrap 'Handset 164', and not the original. That may be at my work and I'll look for it next week.

The handset is ( it think) urea formaldehyde, not Bakelite as I stated earlier, but the profile of the 'Handset No:1' is quite different to the 'Handset No:3' and the section that is held is more like that of a 'Handset 164'. Note the ETL (Ericsson Telephones Limited) logo moulded on.
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Old 30th Dec 2017, 8:40 pm   #48
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Default Re: GEC 1000 phone not working properly?

Forget that last picture, although it would get you fixed up. I found the original rear connection down the shed and have fitted it. It's a springy plate that makes contact with the terminal at the back of the mic, with a grommeted hole in to pass the other mic connection through.
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Old 31st Dec 2017, 1:28 am   #49
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Default Re: GEC 1000 phone not working properly?

If the mic is duff you can remove the plug in unit and the retaining clips, and fit the innards out of the red Tele746 mic on a bed of bubble wrap or foam etc connected to the relevant screws.
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Old 31st Dec 2017, 10:18 am   #50
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Default Re: GEC 1000 phone not working properly?

Quote:
If the mic is duff you can remove the plug in unit and the retaining clips, and fit the innards out of the red Tele746 mic...
Are you on about the electret mic T21A inset, Tim? That's exactly what I had in previously, in the manner you describe!

However, I 'de-converted' back to the original carbon Inset No:13 to show the OP (Bigdaz101) how it was done, as I believe the problem he is having could be related to there being insufficient voltage dropped across his electret mic, and so reversion to the orig. carbon would get around it.

My GEC1000 variant actually works quite well with the original carbon mic so I'll retrieve the T21A mic for future use elsewhere.
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Old 31st Dec 2017, 11:24 am   #51
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Default Re: GEC 1000 phone not working properly?

LOL.
I wonder if it would be possible to prove the electret voltage theory by connecting a 1.5 volt cell- say an AA or AAA in series with the mic and see what happens? The op has a multimeter so he can check the polarity and connect the battery in sympathy.
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Old 31st Dec 2017, 11:43 am   #52
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Default Re: GEC 1000 phone not working properly?

I wondered about that too. As long as the cell or battery used is of sufficiently low impedance to maintain the line loop. Certainly worth a try! Could have a battery box with a capacitor across to reduce the speech impedance path, although a bit convoluted. You'd need to measure the current first as a 'base-line', as the battery would need to drive enough extra current round the loop so that sufficient voltage was dropped across the mic, and the state of the rest of the line resistance (and exchange equipment) is unclear.

Evidently, the line in question is 'miles from anywhere'. I thought I was miles from anywhere but I still manage to draw 40mA round the loop. I don't know how you'd go about reporting a suspected H/R fault to Sky. Perhaps they'd say that 'as long as the line worked' - which, presumably it does on a normal (modern) telephone - there would be nothing they could do about it. They might be a bit 'iffy' about the introduction of a foreign supply into their network! But this isn't a permanent solution we're talking about of course. Oh, no.

As far as the POTS element of telephony is concerned, I've had no experience of repairs or faults other than by BT Openreach.
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Last edited by russell_w_b; 31st Dec 2017 at 12:02 pm.
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Old 31st Dec 2017, 2:08 pm   #53
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Default Re: GEC 1000 phone not working properly?

Cp's can run a test that will show up any HR's.
Any alkaline cell will probably have a low enough impedance to prove the theory.
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Old 3rd Jan 2018, 9:52 pm   #54
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Default Re: GEC 1000 phone not working properly?

Ok today I’m fitted the original mic and on my line it still works fine and it does work on her line but a little muffled my end, I didn’t have a lot of time so I didn’t get chance to check the voltage or try the other phone,
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Old 3rd Jan 2018, 10:58 pm   #55
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Default Re: GEC 1000 phone not working properly?

Could you measure off-hook line current at yours and your mum's? It might be easiest to do this inside the telephone by breaking either red or white wire and inserting a multimeter on milliamperes range. Or connect a 100 Ohm (or similar) resistor in line and measure the voltage across it, hence current.

With the original carbon mic, of course.
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Old 13th Jan 2018, 4:06 pm   #56
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Default Re: GEC 1000 phone not working properly?

Ok tested the voltage today it was 51.6v on hook and 3v off hook, So looks like the problem is low voltage, when I tried my phone the mic worked perfectly but didn’t ring
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Old 13th Jan 2018, 5:08 pm   #57
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Default Re: GEC 1000 phone not working properly?

Quote:
Originally Posted by Bigdaz101 View Post
...but didnít ring
If 'phone is wired for three-wire working (separate wire to ringer), make sure that ringing current is being passed to the ringer wire - via the capacitor in the master socket.
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