SDA's dead tweeters.

deceiver
deceiver Posts: 23
edited December 2005 in Vintage Speakers
I posted this in the troubleshooting page but I thought I might get a wider variety of ideas here.

Hi, I recently fired up a pair of SDA2's. Or at least I think they are that model. Woofer, three midrange and two tweeters in each speaker. I purchased them new in the late 80's/early 90's. Because of a move they hadn't been fired up for a couple of years. They sound great but I noticed that I don't have any sound from the tweeters. I remember you could brush your finger over them and they'd tickle. Now it seems they're dead. I know from the forums that I should do an upgrade on them but, I'd like to get them working first. Is there some kind of tweeter fuse or cutout? They (the tweeters) don't work at all, in either speaker right from power up.

Thanks.
Post edited by deceiver on
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Comments

  • madmax
    madmax Posts: 12,434
    edited December 2005
    There is a polyfuse which may be bad.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
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  • F1nut
    F1nut Posts: 50,729
    edited December 2005
    That model should have a fuse mounted on the binding post plate as the tweeter protection. What can happen over time is that the fuse terminals oxidize and prevent the tweeter circuit from completing. Remove the the fuses, clean the ends and the terminal posts, then try them.
    Political Correctness'.........defined

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  • Loud & Clear
    Loud & Clear Posts: 1,538
    edited December 2005
    F1nut wrote:
    That model should have a fuse mounted on the binding post plate as the tweeter protection. What can happen over time is that the fuse terminals oxidize and prevent the tweeter circuit from completing. Remove the the fuses, clean the ends and the terminal posts, then try them.
    I've experienced this and the remedy as described worked for me. Give it a shot if you do in fact have the external fuses.

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  • nadams
    nadams Posts: 5,877
    edited December 2005
    If you have early SDA2's, they have the fuses mounted externally by the binding posts. If you have the later SDA2's, they have polyswitches.

    Another way you can tell if the tweeter is totally dead or not is to remove it from the cabinet and hook it up directly to y our receiver and see if you get any sound out of it. Start with the volume all the way down and work your way up the volume knob and see if any sound comes out. If you get sound, then you probably need to look somewhere in the crossover for your issues. If no sound comes out... the tweeter is d-e-a-d and you need to contact Polk for the upgraded tweeters.
    Ludicrous gibs!
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  • keith allen
    keith allen Posts: 734
    edited December 2005
    I have the same speakers,but I have no fuses...is it a per year thing,mine are from 85
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  • deceiver
    deceiver Posts: 23
    edited December 2005
    I've got the onesw without the external fuses. I'll have time to take the binding post plate off this weekend. I'll let you know what I find. I hope its as simple as the oxidized fuse thing. But, I was planning on replacing them with the silk domes anyway at some point. Much appreciated. It's amazing how good they sound even without the tweets.
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  • nadams
    nadams Posts: 5,877
    edited December 2005
    deceiver- if you don't have external fuses, then you won't have fuses at all. There will just be a small disc-shaped device soldered on the circuit board. That's what is referred to as the polyswitch. It's a "circuit breaker" of sorts. Sometimes these will fail as they get older. A good way to tell if it's the tweeter or the polyswitch is to do as I detailed above, and connect each tweeter to one of the output channels on your amp (directly) and slowly turn the volume up and see if you get anything. If you get nothing, chances are the tweets are dead. If you get sound, then look to the polyswitch.

    Search for "crossover upgrade" on the forums for details on how to replace polyswitches and caps (might as well do them too while you're in there).
    Ludicrous gibs!
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  • deceiver
    deceiver Posts: 23
    edited December 2005
    nadams wrote:
    deceiver- if you don't have external fuses, then you won't have fuses at all. There will just be a small disc-shaped device soldered on the circuit board. That's what is referred to as the polyswitch. It's a "circuit breaker" of sorts. Sometimes these will fail as they get older. A good way to tell if it's the tweeter or the polyswitch is to do as I detailed above, and connect each tweeter to one of the output channels on your amp (directly) and slowly turn the volume up and see if you get anything. If you get nothing, chances are the tweets are dead. If you get sound, then look to the polyswitch.

    Search for "crossover upgrade" on the forums for details on how to replace polyswitches and caps (might as well do them too while you're in there).

    I am now informed... I now understand.. thanks for the clarification.
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