UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Telephony and Telecomms

Notices

Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment

Closed Thread
 
Thread Tools
Old 15th May 2018, 9:18 pm   #1
Voxophone
Hexode
 
Voxophone's Avatar
 
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
Posts: 340
Default ATM Mining Telephone - Magneto Operation

Hi All,

I’ve recently picked up a bakelite ATM mine telephone (for above ground use) which comes with a magneto. At some point the magneto wiring has been disconnected from the set internally, and I’m not sure how it’s supposed to be connected or how it is intended to function.

The magneto appears to have a number of different terminals and some mechanism which pulses a contact as it is turned. I tried a few test measurements with a DMM to find where the stator coils were likely to be brought out. Measuring here on the AC Volts range I can generate about 15-20 V a.c. when turning the shaft not too strenuously.

I'm guessing the magneto provides the ringing signal while the battery box (which I don't have) holds the line at the required DC voltage?

The base of the unit is marked L11582, which is entered on britishtelephones.com as a magneto telephone but with no information. I have the wiring diagram on the base, which I think may show the magneto in the red circled area photographed below.

Can anyone shed any light on the intended operation of this unit? I’d like to experiment with getting it working, possibly in a stand-alone or intercom sort of arrangement. I’ve attached a couple of photos of the magneto below.

Many thanks

Liam
Attached Thumbnails
Click image for larger version

Name:	DSC_0248.jpg
Views:	135
Size:	123.1 KB
ID:	162948   Click image for larger version

Name:	DSC_0249.jpg
Views:	120
Size:	108.1 KB
ID:	162949   Click image for larger version

Name:	DSC_0250.jpg
Views:	150
Size:	157.6 KB
ID:	162950   Click image for larger version

Name:	DSC_0252.jpg
Views:	141
Size:	157.1 KB
ID:	162951   Click image for larger version

Name:	DSC_0253.jpg
Views:	158
Size:	194.0 KB
ID:	162952  

Voxophone is offline  
Old 15th May 2018, 10:18 pm   #2
russell_w_b
Dekatron
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
Default Re: ATM Mining Telephone - Magneto Operation

The magneto won't 'pulse' the contacts, but will make them as it is cranked and throw them over to the bell cct when stationary. Were you measuring the a.c. voltage on terminals 5 and 3?

The magneto has non-inductive windings to make it intrinsically safe, and this probably accounts for the low a.c. ringing voltage compared to the 75V from a 'Magneto, 26A' as used in (typically) a type F field telephone. I once had a set of intrinsically-safe type 'J' telephones from Haig pit and they had a low magneto voltage too.

The battery is for energising the carbon microphone for the speech circuit.
__________________
Regds,

Russell W. B.
G4YLI.

Last edited by russell_w_b; 15th May 2018 at 10:23 pm.
russell_w_b is offline  
Old 15th May 2018, 10:22 pm   #3
OscarFoxtrot
Heptode
 
OscarFoxtrot's Avatar
 
Join Date: Apr 2011
Location: Edinburgh, UK.
Posts: 805
Default Re: ATM Mining Telephone - Magneto Operation

That's the magneto

Terminals 2-3-4 on it are the 'off normal' contact which changesover when the handle is turned - it doesn't impulse though (or it shouldn't). Usually when the handle of the magneto generator is turned, the bell is disconnected and the generator is connected across the A and B wires. That may be slightly different in a mine phone to avoid any sparks being generated.
OscarFoxtrot is offline  
Old 15th May 2018, 10:44 pm   #4
Alf
Hexode
 
Alf's Avatar
 
Join Date: May 2005
Location: Wigan, Greater Manchester, UK.
Posts: 479
Default Re: ATM Mining Telephone - Magneto Operation

Here's a clearer picture of the circuit diagram, it's also known as the ATM T3903. I get about 20v from the magneto.
Attached Thumbnails
Click image for larger version

Name:	ATM CCT.jpg
Views:	119
Size:	78.5 KB
ID:	162953  
Alf is offline  
Old 8th Jun 2018, 12:25 pm   #5
Voxophone
Hexode
 
Voxophone's Avatar
 
Join Date: Oct 2015
Location: Sunderland, Tyne and Wear, UK.
Posts: 340
Default Re: ATM Mining Telephone - Magneto Operation

Thanks everyone for your advice. Following Alf's diagram, I managed to install the magneto back in the set and it is able to ring an external bell connected to L1/L2.

Regarding the 'impulsed' contact, I can now see that this is not the case. As stated above it disconnects the set's internal bell while the handle is turning.

Next step will be to try it out with a battery over a longer distance.

Out of curiosity, has anyone ever come across one of the below ground ATM telephones which were designed to communicate with this set? (http://www.britishtelephones.com/atm/atmtel6.htm)

Cheers

Liam
Voxophone is offline  
Old 8th Jun 2018, 1:52 pm   #6
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,549
Default Re: ATM Mining Telephone - Magneto Operation

Explosion proof housings are seriously heavy. 83lb for a telephone.
I have seen and handled a CCTV screen for monitoring coal conveyors.
The housing has to be able to contain a CRT with 20KV on the final anode so they are the biggest door stops ever made.
Refugee is offline  
Old 8th Jun 2018, 2:26 pm   #7
Dave Moll
Dekatron
 
Dave Moll's Avatar
 
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
Default Re: ATM Mining Telephone - Magneto Operation

Quote:
Originally Posted by Voxophone View Post
I’d like to experiment with getting it working, possibly in a stand-alone or intercom sort of arrangement. I’ve attached a couple of photos of the magneto below.
If you have (or can gain) access to a field telephone of some sort, this should then work in an intercom arrangement, though how well the low voltage ringing current will work I'm not sure.
__________________
Mending is better than Ending (cf Brave New World by Aldous Huxley)
Dave Moll is offline  
Old 10th Jun 2018, 1:42 am   #8
mickash
Hexode
 
Join Date: Sep 2007
Location: Derbyshire, UK.
Posts: 288
Default Re: ATM Mining Telephone - Magneto Operation

I've also got one of these phones. I keep meaning to get it down from the loft where it's been since we moved here in 2002!

I came across a later version of the underground phone, in Liam's link,in the yard of a closed down pit in the early 1970s. Dad wouldn't let me take it home, just as well really as I couldn't lift it.

A type 405 linesmans phone/field phone should work with your phone Liam.
They can often be found on ebay relatively cheaply.

Michael.
mickash is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:01 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.