SRS 3.1TL SDA Drivers Not Working

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Hansen2112
Hansen2112 Posts: 17
in Vintage Speakers
Just picked up these pristine condition 3.1 sDA speakers from original owner , look brand new. Unfortunately looks like the SDA drivers are not producing any sound , with or without the interconnect cable. Both drivers test good with multimeter , and getting sound out of the other eight drivers. Just the two SDA drivers are not working so I assume it is something in the crossover? I was hoping someone could help identify the problem here, I'm fairly new to speaker repair.

I'm also fairly new to SDA speakers, it's my understanding that the SDA drivers should still produce sound even without the interconnect? With the interconnect cable connected I did test continuity and it is inserted properly. Seems like it should be a pretty easy fix but I'm kind of lost tg293vt4libr.jpg
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  • billbillw
    billbillw Posts: 8,320
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    I would carefully check to make sure all the wiring is correct. Schematic, wiring, and troubleshooting guides are found in this thread:
    https://forum.polkaudio.com/discussion/55888/polk-audio-speaker-wiring-schematics-more-stereo-dimensional-array-sda

    The crossovers could use a refresh/upgrade, but unless there is a broken lead, or cold solder joint, the sound should still go through if wired correctly.
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  • Hansen2112
    Hansen2112 Posts: 17
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    Okay thanks I'll give it a look. Weird that the same sda driver is out in both speakers
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  • WilliamM2
    WilliamM2 Posts: 4,826
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    Have you checked for continuity of the SDA cable? If it's pin/blade, only one wire is used. I replaced mine so long ago with a single terminal, I can't quite remember which, but I believe both will still have continuity.
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  • billbillw
    billbillw Posts: 8,320
    edited October 21
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    Are you sure they aren't playing at a lower level? The SDA drivers play at a reduced level compared to the main stereo drivers.
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  • Gardenstater
    Gardenstater Posts: 4,960
    edited October 21
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    Run through the checks on p 32 of the SDA Handbook (see attachment)

    Attachments aren't working?

    https://forum.polkaudio.com/discussion/136502/sda-handbook?utm_source=community-search&utm_medium=organic-search&utm_term=sda+handbook

    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • WilliamM2
    WilliamM2 Posts: 4,826
    edited October 21
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    Here's a copy if it works.
    Attachments apparently don't work. Here's a lin from Vr3:
    https://www.vr3mods.net/_files/ugd/932cf5_6f335b7f8e3b4ba39613def7f4b3f83e.pdf
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  • Hansen2112
    Hansen2112 Posts: 17
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    Thanks for the attachment to the handbook, that's cool.

    Although I didn't see reference checkpoint numbers for the 3.1's in the handbook to compare, here is what I got. Left has some high readings compared to the right. Also, i removed the SDA drivers and reattached outside of the cabinet and was able to hear sound coming out of the right side faintly , which I think is normal. However still no sound coming out of the left SDA driver. Seems like it must be something in the crossover, any ideas on where to check? Maybe just a bad capacitor? At least I think I narrowed it down to just the left speaker now. By the way, I checked all the wiring by the way, I checked all the wiring to the drivers and everything looks perfect m13cl60vkgxb.jpg
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  • billbillw
    billbillw Posts: 8,320
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    I'm not sure how to exactly interpret the values, but they seem to vary greatly between channels. I'm not an SDA expert, but looking at the photos of each crossover, and the color of the wiring, they seem to be from a different production run. With the right channel speaker having all white wires between the rear terminals and the crossover board, it makes it harder to verify the wiring run.
    I would double check that the tape color around the white cables on the terminals and follow them to the plug and make sure the wires are pinned out correctly compared to the left channel.
    Beyond that, you may need to rebuild the crossovers, which would be a good thing anyway. There should be some good 3.1TL crossover build threads on this forum if you search.
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  • Hansen2112
    Hansen2112 Posts: 17
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    Okay, got it figured out. Took out the crossover and one of the inductors glue became separated from the board and became loose which allowed the lead to pull out. I was able to resolder it back in and now everything seems to be working fine. The resistance numbers now match the right speaker.

    At least now I know how to disassemble everything now which will make it easier once I decide to upgrade the crossover and do any mods.
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  • billbillw
    billbillw Posts: 8,320
    edited October 22
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    One thing I did just notice, is the blue electrolytic capacitor that is squeezed in next to the yellow mylar cap appears to be the wrong value compared to others that I have seen (and for what the schematic shows). It appears you have 12uF caps where they should be 24uF. I am not sure if Polk made a production change during the run. Maybe some others can chime in. Unfortunately, many of the real SRS/SDA experts are no longer posting here for various reasons.
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  • billbillw
    billbillw Posts: 8,320
    edited October 22
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    Glad you found it. Also, I just noticed from your last photo that you have stacked 12uF caps, which is the same as the 24uF that I've seen elsewhere. So disregard my last post.
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  • Gardenstater
    Gardenstater Posts: 4,960
    edited October 22
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    billbillw wrote: »
    One thing I did just notice, is the blue electrolytic capacitor that is squeezed in next to the yellow mylar cap appears to be the wrong value compared to others that I have seen (and for what the schematic shows). It appears you have 12uF caps where they should be 24uF. I am not sure if Polk made a production change during the run. Maybe some others can chime in. Unfortunately, many of the real SRS/SDA experts are no longer posting here for various reasons.

    I see that too. The schematic we have is 5/3/1990 and is Rev. A. Maybe there was a Rev. B after that one and we don't have that schematic. What is the date on the binding post cup? It is cut off in the photo.

    Edit - Yeah I see that they are stacked now too. Wasn't immediately obvious for sure.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on Facebook