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Thread: SDA-CRS Repair

  1. #1

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    Default SDA-CRS Repair

    Help SDA experts. I am the original owner of circa 1984 SDA-CRS's. Up until a recent flood, they have performed perfectly. My sump pump broke and I wound up with a couple of inches of water in the basement theater. The system was on (not playing, but powered on) and the speaker wires and interconnect cable were submersed for a few hours. System was uninstalled floor dried and system reinstalled. Upon power up, speakers output a loud oscillating hum. Immediate power down and troubleshooting of wires, etc ensued. Removal of interconnect cable solved the problem and system operated as normal except for expected loss of output from dimensional driversand SDA effect.
    Inspection of interconnect showed some cracks and holes in the insulation, probably from my trying to shove it under the baseboard and the carpet tacks penetrating the insulation. I tried to build a new interconnect using information from this forum, but still have the same problem with the loud hum. I expect this is a crossover problem in one or both of the speakers, eithier due to age or a short due to the flood.
    I don't have any type of multimeter or skill in using one, I assume I would have to test the crossovers somehow. Can someone walk me through this? I have zero soldering skills, so rebuilding a complex crossover is probably not something I can do.
    To tell the truth, they still sound great, but I know in my mind that they are not performing as well as they should. If it is more work than I am able, I may just sell them and move on to something else.

    Any help would be appreciated.

    Vectordirector

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    Welcome to Club Polk vectordirector!!!

    You've definitely come to the right place. I own a set of CRS's and I love them. There are many, many gurus here who can help you with everything from xovers all the way to revaneering them. Hang on and I'll give you a bump up to the top here so that other can help you out.

    Joe

    BTW Mine have the Rd0194 tweeters and vampire binding post with a beautiful veneer job done by F1nut. YOu will be bless if Jesse (F1nut) see this and chimes in.,

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    Could'nt the amp be the problem too? The hum is only when the SDA cable is connected completing the circuit.

    I am probably wrong but for s&g I would try a differnt AMP before ripping the XOs out.
    Speakers: SDA-1C (most all the goodies)
    Preamp: Joule Electra LA-150 MKII SE
    Amp: Wright WPA 50-50 EAT KT88s
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    Ofc: Wright WLA12 preamp: Anthem Amp 1: Pio Elite DV-79AVI: Airport Express: CAL Sigma II DAC: PA LS90 sonicaps and mills

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    You say that both speakers work well without the interconnect?

    If yes, and putting in the interconnect causes a hum, then the first thing I would check is the polarity of the connection from the speakers to the amp. Make sure positives (reds) go to positives (reds) and negatives (black) to negatives (black). Make absolutely certain of this.

    Now if you still get the oscillation when you put in the interconnect, then please describe the sound - does it sound like a mains frequency hum? high pitched? can you be more descriptive?

    I'm thinking its most likely you just rewired it back incorrectly. I doubt the crossovers would suddenly fail as the speakers were not submerged. Same with the amp. If it was not exposed to water, then unlikely to be the issue.

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    Thanks for the replys. I've been doing this for 30 years and know what I'm doing. I'll be the first to admit hooking something up wrong. We have all done it , especially when in a hurry. That being said, I checked the connections again and all is as it should be. I'm running without the interconnect. Nothing other than the cables got wet. Amp is an Outlaw 7125 (7x200@4ohms) and has been driving this system for over 6 years without issue.
    I wish I could describe the sound. It is like a mains hum but really loud, no matter what volume the system is at. I'm no electrical engineer but it sounds like the amp is going into oscillation and playing a waveform, square, sine, sawtooth maybe, I don't know. Sounds like a lower frequency euro ambulance. dee-dah dee-dah but maybe around 100hz and probably at full power. It hasn't blown the fuses on the speakers, because I immediately unplug it. I don't hear it in my sub which is sent from the prepro (outlaw 990) via xlr crossed at 80Hz. I unplugged the sub output thinking it was a ground loop but it didn't matter. I guess I'll try another amp and see what happens. Anybody know if a Behringer EP1500 ( my sub amp) is common ground?

    Vectordirector

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    Quote Originally Posted by vectordirector View Post
    Thanks for the replys. I've been doing this for 30 years and know what I'm doing. I'll be the first to admit hooking something up wrong. We have all done it , especially when in a hurry. That being said, I checked the connections again and all is as it should be. I'm running without the interconnect. Nothing other than the cables got wet. Amp is an Outlaw 7125 (7x200@4ohms) and has been driving this system for over 6 years without issue.
    I wish I could describe the sound. It is like a mains hum but really loud, no matter what volume the system is at. I'm no electrical engineer but it sounds like the amp is going into oscillation and playing a waveform, square, sine, sawtooth maybe, I don't know. Sounds like a lower frequency euro ambulance. dee-dah dee-dah but maybe around 100hz and probably at full power. It hasn't blown the fuses on the speakers, because I immediately unplug it. I don't hear it in my sub which is sent from the prepro (outlaw 990) via xlr crossed at 80Hz. I unplugged the sub output thinking it was a ground loop but it didn't matter. I guess I'll try another amp and see what happens. Anybody know if a Behringer EP1500 ( my sub amp) is common ground?

    Vectordirector
    If your sub amp is a single channel then yes it is common ground. However it may not be on common ground with your other amplifier used to connect to the speakers. That being said be very careful.

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    I am guessing there is water in the interconnect cable and it is causing a short.
    Quote Originally Posted by Timothy Smith View Post
    WOW!

    That's like working your way through Katie Perry in order to get to Rosie O'Donnell.

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    Quote Originally Posted by vectordirector View Post
    Anybody know if a Behringer EP1500 ( my sub amp) is common ground?
    It is as long as it 's not used in bridged mono mode.

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    I'll try another amp sometime soon and see what happens. I'll remember to reset the Behringer to stereo. I built a new interconnect using the ends from the old one. Didn't make a difference. I have to recheck the wiring of the new interconnect to make sure I did it right. Common ground is straight or crossover? I can't find the post with the information.

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    Strange indeed. Yes it does sound like the amp is going into oscillation. Amps usually do that when there is some problem with the grounding, or there is a ground loop forming of some sort. I cannot for the life of me figure out how it would be forming a ground loop if the amp is common ground.

    Since you have already hacked up that interconnect cable, you could try just connecting the center pin (leave the other portion of the interconnect open i.e. do not connect it). This is assuming you have a pin-blade interconnect. If just connecting the center pin gives you back the SDA effect with no oscillation, then you have some sort of issue going on with that amp most likely.

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    Actually it is a blade/blade. These are very early CRS's purchased in mid 1984. Still searching for information on the wiring of that cable. Hopefully finding time this weekend to try a different amp. I'll keep everyone advised.

    Thanks again all.

    vectordirector

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    Wide blade to wide blade, narrow to narrow.
    'Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

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