SDA 1 crossover Fuzes?

sswilson
sswilson Posts: 13
edited August 2008 in Vintage Speakers
Hi folks...

Complete newb to the forum and like the newbs over in the computer forum I mod at I'm showing up with a technical question hoping you fine folks can help me out.

I've owned a set of original SDA 1 speakers since `88 and during a recent move the left speaker high end gave out.

I've downloaded the schematics from this site (thanks tons for that!!!) and had an initial look at the crossover module, but haven't actually managed to get it out of the cabinet yet.

First question......

The schematic shows a few fast blow fuzes, but I can't for the life of me see them on the PCB while it's still installed in the case.

Are these located somewhere on the PCB and I'm just not seeing them? Are they a standard metal capped glass fuze?

Second question....

I've noticed that the PCB is mounted (with those hateful plastic "pinch" standoffs) to the wire wound spool at the back, but that the spool appears to be attached by a single screw on the back of the case... does anybody out there know for sure if the screw can be easily replaced if it's removed to get the whole thing out as a unit? (I think that's the way I'm going to approach it, but I'll be kicking myself if it's a major PITA to get back on).

Third (and hopefully last for now) question....

I've tested the tweeters by removing the plug from the PCB and can verify that there is audio coming through both of them, but it's at least 1/10 the volume of the r/h speaker.

I know it's not much to go on, but does that cause a lightbulb to go off in anybody's head as to what the problem might be?

I've got a bit of electronics training, but my work background is mainly electrical/mechanical so component level faultfinding is certainly not my strong point.

Anywise... thanks in advance for any info you might be able to give me.
Post edited by sswilson on

Comments

  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    First welcome to Club Polk.
    Second if your SDA's have fuses they are located on the outside. Most likely they have poly switches on the PCB. Try swapping the "bad" tweeters into the good tweeters cabinet. This will tell you if the tweeters went bad, or the Poly switches. If the tweeters work fine in the other cabinet then you know the tweeters are good. Also the outer tweeters are not as loud as the inners, and you may not even be able to hear them without the IC cable installed. You do have the cable that goes between the two speakers correct?
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • sswilson
    sswilson Posts: 13
    edited August 2008
    Thanks for the suggestions. I'll swap out the L/R tweeter cables in the morning to verify the tweeters are actually working.

    The original SDA1s didn't have an "inner & outer" tweeter. They're mounted one on top of the other dead center of the cabinet.

    I do still have the interconnect cable, and tested with it installed and removed with no change.

    What do you mean by "poly switches"? Is that a resetable fuze?
  • sswilson
    sswilson Posts: 13
    edited August 2008
    Hrmmmmmm....

    Now that I'm looking around, I'm not sure what model SDA1s I've got.

    I assumed the "C" would be included in the part# but mine look exactly like these http://www.polksda.com/sda1c-studio.shtml and I notice the backplate in the images there don't discriminate between what model it is....

    Is there an easy way to tell? (ser#s on mine are 10914 & 10807)
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    Tweeters one on top of each other would be 1b's, or c's;)
    On the back where the IC cable plugs in does it have a round pin, and a flat connector, or two flats? BTW you have no fuses.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • Disc Jockey
    Disc Jockey Posts: 1,013
    edited August 2008
    Like ben said, you most likely have an internal protection poly switch which automatically resets after being tripped. If it doesn't or if it trips too early, you need to replace them. If you post pics, your version can be identified by the folks here. Schematics are available here for the crossover.
    "The secret of happiness is freedom. The secret of freedom is courage." Thucydides
  • sswilson
    sswilson Posts: 13
    edited August 2008
    I have a round and a flat plug for the interconnect cable.

    I'll try to post some pics up tomorrow.

    Thanks for the link to the schematics, but it's not doing me any good until I can figure out what actual model I've got... ;)
  • Disc Jockey
    Disc Jockey Posts: 1,013
    edited August 2008
    sswilson wrote: »
    Thanks for the link to the schematics, but it's not doing me any good until I can figure out what actual model I've got... ;)

    Well, if you take your speaks apart and compare the crossovers to the schematics it might help a bit...:D
    "The secret of happiness is freedom. The secret of freedom is courage." Thucydides
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    You have 1C's ;)
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • sswilson
    sswilson Posts: 13
    edited August 2008
    Heh...

    Ok it's a "C" model. (I did actually get the crossover module out).

    Does Polk still sell crossover units for these? I suspect I can't just replace one component without completely changing the sound, and because of that would I need to replace both crossover.

    (Please be easy on me... :) ).
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    If you are handy with a soldering iron you can fix it with a little guidance. Plenty of good people to help here. Where are you located?
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • sswilson
    sswilson Posts: 13
    edited August 2008
    I'm down in Moncton New Brunswick.

    It's getting kind of late here so I'm going to place everything on a shelf for the night before I muck something up... :)

    (Not really sure I've got the equipment to actually test component level...... ).
  • sswilson
    sswilson Posts: 13
    edited August 2008
    Good morning again. :)

    I've done some testing and verified that the tweeters are indeed fine so now it's down to trying to faultfind the crossover at the component level.

    SDA 1C Crossover S1.jpg



    Since I can hear some output from the tweeters (albeit quite muted) my first inclination is to look at the overvoltage protection RXE135 but I can't find that identifier on any of the components.....

    Am I correct in assuming that S1 (circled in the above picture) is this component? If it is, can I safely jumper it (at low amp volumes) to test the component?

    Here's an unaltered pic of the PCB if somebody wants to use it to point out components to me.

    SDA 1C Crossover.JPG


    Once again, thanks in advance.
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    You got it! Replace that little mustard colored disk with a jumper, and there is a 90% chance you are back in business(be smart with the volume!). I have had partial failures of those components, and total failures.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • heiney9
    heiney9 Posts: 24,158
    edited August 2008
    sswilson wrote: »
    T
    The original SDA1s didn't have an "inner & outer" tweeter. They're mounted one on top of the other dead center of the cabinet.

    I do still have the interconnect cable, and tested with it installed and removed with no change.

    What do you mean by "poly switches"? Is that a resetable fuze?

    You don't have "original" 1's as the first and second gen SDA 1's and SDA 1A had side by side tweeters where the outer tweet was also on the dimensional circuit. The later 1B's and 1C's had the tweeters stacked and arranged in a progressive point source array.

    It sounds like you have 1B's (which is good) and they use a resetable "poly switch" which is located on the pcb and is either brown or blue or even yellow. The poly switches start to become less effective over time and need to be replaced. Polk will usually supply those for free if you just ask.

    Hope this helps

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • sswilson
    sswilson Posts: 13
    edited August 2008
    Success!!!!

    I'm tickled pink! That solved the problem so now I'm on the hunt for a local business that can supply a replacement.

    Thanks for all the help!
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    Brock they are 1C's
    No need to find a replacement for the Poly switch if you use caution. The SQ is actually better with the jumper. You need to not crank the stereo into distortion thats all;) If you want the correct Poly switch contact Polk CS, and let them know you are a member. They will usually ship replacements for free:)
    Ben

    Edit local stores will not have the proper poly switch unless you live near Madisound, or Parts Express.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • heiney9
    heiney9 Posts: 24,158
    edited August 2008
    sswilson wrote: »
    Success!!!!

    I'm tickled pink! That solved the problem so now I'm on the hunt for a local business that can supply a replacement.

    Thanks for all the help!

    A replacement for the poly switch? You can get that from Polk for free it just takes a call to Customer Service and I bet you'd have them by weeks end.

    Or, are you in a hurry to get this done right now!

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • heiney9
    heiney9 Posts: 24,158
    edited August 2008
    ben62670 wrote: »
    Brock they are 1C's

    After studying the x-over I see that now. sswilson, these are the last gen SDA 1's and are the most desirable. So take care of them and they will sound wonderful. IMO, one of the best in the whole SDA line unless you have an unusually large listening area, then the big boys would really shine. :)

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    heiney9 wrote: »
    After studying the x-over I see that now. sswilson, these are the last gen SDA 1's and are the most desirable. So take care of them and they will sound wonderful. IMO, one of the best in the whole SDA line unless you have an unusually large listening area, then the big boys would really shine. :)

    H9

    Great minds think alike :p
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
  • heiney9
    heiney9 Posts: 24,158
    edited August 2008
    I also have to advocate upgrading/refreshing those 20 year old x-overs since you have them all apart. It will take your 1C's to a whole other level. Do a search and you will see many have successfully refreshed their x-overs and are extremely happy.

    And might as well add that there is a replacement tweeter (RD0194-1) that is much smoother and has much less resonance and gets rid of the nasty 5dB spike at 15kHz that the original sl2000 exhibits.

    Of course if you are completely satisfied with the original tweets then maybe you don't need to upgrade the tweets. It does however in my opinion and almost every other person's who has used them make a HUGE difference in accuracy and make the 1C's that much more enjoyable.

    Ok, I'm done giving advice but atleast keep it in mind as you search around the site you'll see many have gone down this path with great results and success.

    Welcome, good luck and enjoy your speakers as well as all the great people here.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • sswilson
    sswilson Posts: 13
    edited August 2008
    heiney9 wrote: »
    I also have to advocate upgrading/refreshing those 20 year old x-overs since you have them all apart. It will take your 1C's to a whole other level. Do a search and you will see many have successfully refreshed their x-overs and are extremely happy.

    And might as well add that there is a replacement tweeter (RD0194-1) that is much smoother and has much less resonance and gets rid of the nasty 5dB spike at 15kHz that the original sl2000 exhibits.

    Of course if you are completely satisfied with the original tweets then maybe you don't need to upgrade the tweets. It does however in my opinion and almost every other person's who has used them make a HUGE difference in accuracy and make the 1C's that much more enjoyable.
    Ok, I'm done giving advice but atleast keep it in mind as you search around the site you'll see many have gone down this path with great results and success.

    Welcome, good luck and enjoy your speakers as well as all the great people here.

    H9

    Thanks for the suggestions, I'll consider upgrading at a later date, but as it stands I'm quite pleased with the current output.

    The only thing I'm looking at now is either getting a replacement polyswitch, or jumpering the R/H crossover as well. I find the set is slightly unbalanced on the high end with the L/H jumpered and the R/H not.

    That said..... I just slapped on some Chemical Brothers and the sound quality out of them is something I haven't heard from my SDAs in quite some time... It's a new room so that's part of it, but it also makes me wonder how long that Polyswitch has been on the way out.
  • ben62670
    ben62670 Posts: 15,969
    edited August 2008
    Polyswitchs fail slowly over time. I will second the upgrade. Its not a lot of coin to do yours, and it makes a huge difference.
    Ben
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben