#1
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majestic 130 speaker
I want to test this speaker,i don't have the radio.i wanted advice so I don't ruin it..any help is appreciated. .thanks Doug
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#2
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Use a DMM in ohms mode to check continuity.
If it is a field coil type you could tap into a 250-450V radio B+ to power the field (put a 150mA dial lamp in series with it to act as a fuse), and then drive the voice coil with the radio's speaker connections.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#3
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I appreciate the response. It appears to have a coil on back the speaker and under it.maybe in parallel along with voice coil...not normally what I have seen before with electro magnets.this thing is quite bulky .
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#4
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Some field coil speakers had 'hum bucking coils' wound on the field coil....They would magnetically pick up the unwanted AC field in the field coil and feed it back to the voice coil 180 degrees out of phase thus cancelling any hum generated in the field coil.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#5
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It could be a coil to cancel out hum, however another (more likely) possibility is that the audio output transformer may also mounted on the speaker. If this is the case then the B+ is connected to one side of the primary of the audio output transformer and the other side goes to the plate(s) of the audio output tube(s). Then the secondary of the transformer reduces the impedance to the voice coil somewhere between 2 to 8 Ohms. Some detailed pictures would help a lot. Ohm-ing it out can tell you a lot also. Also another thing you can do is gently push on the center of the speaker and if you feel the voice coil rubbing, that's not a good thing. It should move freely without any scraping sound sound or feel. All the speakers with field coils that I have seen have the hum cancelling winding embedded within the field coil, so most likely the extra "coil" (transformer) is an audio output transformer. As mentioned above put a DC current through the field coil, and the voice coil to the audio output of a radio, etc. Maybe use a variable DC supply to supply current to the field coil. A bulb in series is a good idea so you don't accidentally fry the field coil. If it sounds good at low and high volumes, you've got a good speaker!
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Audiokarma |
#6
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It's a 'pin drive' speaker that doesn't use an output xfmr. If the winding has continuity and the speaker still doesn't work, the 'armature' might be rusted solid. See vid beginning at 2:55.. https://www.youtube.com/watch?v=9yiNMrsmikk
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#7
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Seems like a lot of stuff going on around that speaker.
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#8
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Hells bells looks like there's a different "model 130".
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#9
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Boy was I wrong! I have never seen a speaker like that, like the one shown in the video. Basically the output drives the speaker directly without an output transformer or voice coil. Yea, probably only a couple of things can go wrong, the pin that drives the speaker could be corroded and frozen up, or the coil could be open. Probably quite efficient, however I would think very low fidelity.
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