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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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3rd Feb 2015, 4:07 pm | #1 |
Hexode
Join Date: Oct 2010
Location: Box End, Beds. UK.
Posts: 271
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Malfunctioning external bell unit
A colleague has a large telephone bell, suitable for external use which does not work, apparently because the central permanent magnet has lost some of its magnetism. Is this diagnosis plausible, and if so, are there any suggestions as to how to remagnetise it?
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3rd Feb 2015, 4:41 pm | #2 | |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,687
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Re: Malfunctioning external bell unit
Quote:
Has the wiring been tampered with? The left-hand terminal of one bobbin should be connected to the left-hand terminal of the other with the bell-wires connected to the right-hand terminals. Or the other way round, NOT linked left-to-right or right-to-left. I suspect it will be a type 59A bell motor, which are pretty common if you wish to replace it. The modern type 59A bell-motor has a small bar-magnet mounted under a clamp and the older unit has a cylindrical magnetic bar between the bobbins. See here. If you've tried all the above and feel you need to remagnetise the cylindrical bar, remove it from the yoke, wrap about twenty turns of 1.5mm wire around it and 'flash' it on a car battery for a second or two (but wear eye protection!).
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Regds, Russell W. B. G4YLI. |
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