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Electrical advice - old fire alarm bell
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<blockquote data-quote="Perplexed" data-source="post: 3834144" data-attributes="member: 7157"><p>Guess no one has any suggestions per my last post. But here’s a related issue to ponder, if you wish…</p><p></p><p>I have another fire alarm bell, constructed in a similar fashion, but which has an odd behavior when I apply 6V DC. The wires coming out of the electromagnet (EM) assembly go to Posts A and B, with the interrupter contact on Post B. Yet, when I attach the power leads to these posts and apply power, the clapper is drawn to the EM and held in place with no further movement, despite the interrupter contact being broken. I can see the contact is indeed broken via a visual inspection - there’s a definite gap between the contact on Post B and the spring steel extension coming off the clapper arm. Backing the contact out some more does nothing. When I cut the power, the clapper is pulled back by the spring. If I attach the leads to Posts A and C, the alarm functions normally with the clapper repeatedly striking the bell. Post C seems to have no wired connections at all with anything else - it’s just a raised extrusion of the base with a threaded screw in the top, so I don’t see why it should have any function. Anyone know why this might be so?</p><p></p><p></p><p></p><p>[ATTACH=full]292808[/ATTACH]</p><p></p><p>[ATTACH=full]292809[/ATTACH]</p></blockquote><p></p>
[QUOTE="Perplexed, post: 3834144, member: 7157"] Guess no one has any suggestions per my last post. But here’s a related issue to ponder, if you wish… I have another fire alarm bell, constructed in a similar fashion, but which has an odd behavior when I apply 6V DC. The wires coming out of the electromagnet (EM) assembly go to Posts A and B, with the interrupter contact on Post B. Yet, when I attach the power leads to these posts and apply power, the clapper is drawn to the EM and held in place with no further movement, despite the interrupter contact being broken. I can see the contact is indeed broken via a visual inspection - there’s a definite gap between the contact on Post B and the spring steel extension coming off the clapper arm. Backing the contact out some more does nothing. When I cut the power, the clapper is pulled back by the spring. If I attach the leads to Posts A and C, the alarm functions normally with the clapper repeatedly striking the bell. Post C seems to have no wired connections at all with anything else - it’s just a raised extrusion of the base with a threaded screw in the top, so I don’t see why it should have any function. Anyone know why this might be so? [ATTACH type="full"]292808[/ATTACH] [ATTACH type="full"]292809[/ATTACH] [/QUOTE]
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