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Electrical advice - old fire alarm bell
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<blockquote data-quote="Perplexed" data-source="post: 3846014" data-attributes="member: 7157"><p>Ok, here’s another one that has had me stumped for a while...</p><p></p><p>I have this antique bell with two electromagnets, and the wires from each end of the EM’s are as shown on the underside - this is the way it came to me, but I had to rewire the EM’s because the rig in the past apparently had gotten too hot and the wrap around each EM had melted. I tested each newly wound EM using a variable DC power supply, and both were good. 6V DC and 12V DC, 2-3 amps, proved to work by pulling steel objects toward them. I tested the EM’s again after linking them, and again both were good. The end caps were made from Delrin. I mounted the two EM’s directly to the frame as in the original, and tested them by connecting the DC power to the ends of the two wires. They pulled the arm of the clapper to them, as expected. Then I connected the ends of each wire as shown in the pics (A and B), using shrink tubing as an extra insulator, and I tried testing by touching the power leads to the post at A and the bracket that holds the clapper arm (B), but got nothing. No response. I tried one lead on A and then the two knurled knobs at C and D, and one lead on B and then C and D, but nothing. Now I’m wondering (1) if the bolt that holds the (A) post in place from underneath should be electrically isolated where it passes through the steel base, and (2) what the knurled knobs at C and D are for, since I can’t see how they are connected to the circuit unless a wire or two is missing that bridges C or D to either A or B. I’m assuming the two knurled knobs are for the power leads, but again, I’m not sure how they’re connected to anything else unless it’s via the steel base. I do have a multimeter, but I’m not exactly sure how or where I should be measuring resistance on this setup other than to confirm the two EM’s are connected properly to each other. Any tips from you electrical wizards would be appreciated!</p><p></p><p>[ATTACH=full]297653[/ATTACH][ATTACH=full]297654[/ATTACH]</p></blockquote><p></p>
[QUOTE="Perplexed, post: 3846014, member: 7157"] Ok, here’s another one that has had me stumped for a while... I have this antique bell with two electromagnets, and the wires from each end of the EM’s are as shown on the underside - this is the way it came to me, but I had to rewire the EM’s because the rig in the past apparently had gotten too hot and the wrap around each EM had melted. I tested each newly wound EM using a variable DC power supply, and both were good. 6V DC and 12V DC, 2-3 amps, proved to work by pulling steel objects toward them. I tested the EM’s again after linking them, and again both were good. The end caps were made from Delrin. I mounted the two EM’s directly to the frame as in the original, and tested them by connecting the DC power to the ends of the two wires. They pulled the arm of the clapper to them, as expected. Then I connected the ends of each wire as shown in the pics (A and B), using shrink tubing as an extra insulator, and I tried testing by touching the power leads to the post at A and the bracket that holds the clapper arm (B), but got nothing. No response. I tried one lead on A and then the two knurled knobs at C and D, and one lead on B and then C and D, but nothing. Now I’m wondering (1) if the bolt that holds the (A) post in place from underneath should be electrically isolated where it passes through the steel base, and (2) what the knurled knobs at C and D are for, since I can’t see how they are connected to the circuit unless a wire or two is missing that bridges C or D to either A or B. I’m assuming the two knurled knobs are for the power leads, but again, I’m not sure how they’re connected to anything else unless it’s via the steel base. I do have a multimeter, but I’m not exactly sure how or where I should be measuring resistance on this setup other than to confirm the two EM’s are connected properly to each other. Any tips from you electrical wizards would be appreciated! [ATTACH type="full" alt="E9496D1A-6119-45DA-BC46-F647C0905736.jpeg"]297653[/ATTACH][ATTACH type="full" alt="8260A3DD-EE00-44A8-8DDF-1041981F0A7F.jpeg"]297654[/ATTACH] [/QUOTE]
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