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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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12th Mar 2016, 11:07 am | #1 |
Rest in Peace
Join Date: Apr 2012
Location: West London, UK.
Posts: 665
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Entryphone problem
Hi, each hallway in the estate where I live has (audio only) Entryphones installed. These have 4 functions:-
a) Buzzer b) Door Open c) (combined) Mike/Speaker On some (c) have ceased functioning. These are located in the Buzzer Push Panel, outside, by the main front door. Each serves 6 flats and as all flats have same problem, I thought (c) to blame, and failure probably due to age, being around 30 year sold. Is there a way to test these, other than swapping out - e.g.with a meter? Operating voltage for system is 12 volts. Thanks - Mike Last edited by AC/HL; 12th Mar 2016 at 4:17 pm. Reason: Thread split |
12th Mar 2016, 8:55 pm | #2 |
Octode
Join Date: Jan 2013
Location: Barnsley, South Yorkshire, UK.
Posts: 1,517
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Re: Entryphone problem
Are these the Farfisa ones? If so these are often wired so that although a caller presses and alerts say flat 6 if, by chance a neighbour in another flat picks up the receiver in their flat at the same time they can speak to the front door. This then proves the 'entrance end'. Chances are if all the other functions work but speech has failed on one or two flats make sure the receivers at the flat end aren't at fault; if they're on-hook handset types, has the cord failed? etc
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12th Mar 2016, 9:11 pm | #3 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Entryphone problem
The ones I'm familiar with are extremely crude - a carbon mic, a single-transistor amplifier (usually something like an AC128) and a small, cheap, relatively-high-impedance (35-80 Ohm) speaker - they don't usually bother with an output transformer and put the speaker directly in the collector circuit of the transistor amp (a few tens of milliamps doesn't pull the cone too much one way or another: remember we're not after hi-fi here!)
Usual failures I've seen are the speaker cones disintegrating through age/spiders/woodlice/mould/damp, and the speaker-magnets going rusty (damp again!) and swelling so the voice-coil can't move. Finding new high-impedance speakers is hard these days. |
13th Mar 2016, 1:30 am | #4 |
Dekatron
Join Date: Jul 2008
Location: Charmouth, Dorset, UK.
Posts: 3,601
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Re: Entryphone problem
I installed a four way one some considerable number of years ago which slowly lost its functions and it was caused mostly by moisture ingress corroding the connecting wires.
Peter |
13th Mar 2016, 11:27 am | #5 |
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Join Date: Apr 2012
Location: West London, UK.
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Re: Entryphone problem
Hi thanks for your replies.
Nick - you are correct, that when working normally, any flat can pick up their handset and listen to or speak with the front door As I understand the problem, (a) and (b) work for ALL 6 flats (c) does NOT work for ALL 6 flats. This leads me to think the combined Mike / Speaker, being common to all flats, is at fault. Hence my query if there was a simple way to prove this, other than swopping out. The system was manufactured by Safnat of Milan, who no longer exist. This is disappointing as I visit Milan occasionally and wanted to query if they had an indicating (with light) handset, as another problem is a number of residents have hearing problems, causing difficulty hearing the Buzzer. Thanks - Mike Last edited by mike_newcomb; 13th Mar 2016 at 11:30 am. Reason: Spellin Correction :-) |
14th Mar 2016, 12:36 am | #6 |
Octode
Join Date: Jan 2013
Location: Barnsley, South Yorkshire, UK.
Posts: 1,517
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Re: Entryphone problem
Just a thought, but is it just a co-incidence Safnat and Farfisa are both Italian companies? I'm just wondering if Safnat were bought out by or were always a division of Farfisa; in which case diagrams or spares may still be available.
If you're lucky it might just be damp & age that's got to the mic/speaker. If it's like the one we have here just be mega-careful when taking the front off; a tangle of very thin, single core & quite corroded wires lurk ready to spring off. |
14th Mar 2016, 1:20 am | #7 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
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Re: Entryphone problem
Most doorphone systems of the pre-chinese era I've seen have been italian. It's one of their things.
I'd suspect corrosion or water ingress in the main door intercom if it's at all exposed.
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Kevin |
14th Mar 2016, 12:23 pm | #8 |
Rest in Peace
Join Date: Apr 2012
Location: West London, UK.
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Re: Entryphone problem
Hi, there is no evidence of water or damp, either inside or outside of the main door units.
This is because they are sheltered within a Porch area. Returning to my query, is there a way to test these mike / speakers , other than by swapping out - e.g.with a meter? Thanks - Mike Last edited by mike_newcomb; 14th Mar 2016 at 12:28 pm. Reason: Correction |
14th Mar 2016, 1:15 pm | #9 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
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Re: Entryphone problem
You could get one of the working units, disconnect it, then measure the mike and speaker with a resistance meter to see what they read.
The speaker/receiver will probably be a moving-coil device with a lowish resistance, and could be tested by feeding it from a personal stereo, signal generator or similar. The mike/transmitter could be similar, but it could be a carbon, crystal or electret/condenser type. The method of testing would depend on which, I suppose. Could you post some pics of the transducers? You could of course swap just the mike or speaker to prove that the rest of the station and its wiring is OK. Nick. |
15th Mar 2016, 7:50 pm | #10 |
Heptode
Join Date: Apr 2011
Location: Edinburgh, UK.
Posts: 805
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Re: Entryphone problem
If you can, check the power supply at source and at the speech unit. Similar systems often use 12 Vac for the buzzer and lock release, but the speech unit will need dc and there may be a blown fuse on the dc supply.
These systems are fairly standard - terminals on Safnat phones compared to a universal replacement: Lock, microphone, common, speaker, buzzer Safnat 4 1 2 3 V Entryphone 3 P F/B/G L A http://www.louis-grace.co.uk/pdfs/FE3399.pdf |
15th Mar 2016, 7:53 pm | #11 |
Heptode
Join Date: Apr 2011
Location: Edinburgh, UK.
Posts: 805
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Re: Entryphone problem
You can get strobe lights activated by a 12 Vac or dc trigger eg
http://videx-security.com/products/d...t-strobe-unit/ additional/local 12V power supply needed. |