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Post by The Mad Norseman on Feb 15, 2014 14:45:44 GMT -5
I've got a problem with my right subwoofer that's been starting to occur over just the last week or so...where it doesn't kick in when fed it's low frequency signal. This is a JBL ES250P, 12" subwoofer with 400w RMS amp. I'd notice the red LED light on and go over and check the connection (good), and 'jiggle' the RCA cable at the LFE input a bit and it would then 'spring to life', only a few minutes later reverting back to the red LED signifying 'no signal'. I did some more experimenting today and ruled out the pre-amp (signal being sent), and ruled out the strength of the signal being delivered (no changes, and just to experiment I upped the gain temporarily - also to no effect). I also ruled out the cable itself as being the culprit. But as before, I can get it to work (temporarily) by pulling out the RCA cable and re-inserting, or often just 'jiggling' it... I noticed today that I can maintain a constant signal by exerting some downward pressure on the RCA cable connecting to the subwoofer (I've now rubber banded that to the power cord connection below to maintain that downward pressure slight angle). But that's hardly a satisfactory, or long term solution! Any ideas as to exactly what the problem might be? Loose internal RCA connection inside the back plate of the subwoofer maybe? IF so, it that something I could re-solder myself I wonder??? Ideas anyone?  |
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Post by The Mad Norseman on Feb 16, 2014 11:42:44 GMT -5
A Sunday 'Help Bump'...ideas anyone???
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Post by Boomzilla on Feb 16, 2014 11:58:14 GMT -5
The connection has become loose inside the plate amp on that RCA jack. If you can solder, pull out the plate amp and have a look. The socket's outside jacket should be firmly grounded, and the tip wiper & its connection should have a clean, shiny hot solder joint. If the soldered connection is dull or cracked looking, then either the factory had a "cold solder joint," or the connector has failed from mechanical stress over time. Occasionally, the tip wiper (that usually relies on the springiness of the steel connector to wipe the tip of the RCA plug) has just become fatigued and no longer makes as good a connection as it once did. Occasionally, you can bend that wiper back so that it has better tension, but often, you can't get to it at all.
If necessary, you can buy a new (and probably better quality) jack from either Parts Express or Radio Shack & install it in place of the original.
I wish I could give you better news, but from what you describe, it sure sounds like a mechanical problem with the jack. The sure telltale is that you can sometimes jiggle the connector & get it to work.
Best of luck with it - If you lived nearby, I'd be happy to drop by & solder in a fresh jack for you, but that proximity isn't likely.
You might also check to ensure that the "leaves" of the ground on the RCA plug are making good contact with the socket. You can have no sound from EITHER loss of ground OR loss of signal. Sometimes the leaves of the male plug (particularly if it's a cheap or fancy cable) can be either too flexible (cheap cable) or too rigid (fancy cable) to make good contact. If they don't make a firm contact with the input socket, then you get no sound. I've had to take a pair of pliers before & compress the outer leaves of the male RCA plug to make them hook up consistently. Also, if the input socket is not clean, you can get enough dirt/corrosion on it to prevent contact. The socket should be clean & shiny looking. If it isn't then go to Wal Mart or any hardware store & buy a can of "Nevr-Dull." A pinch of the cotton wadding will clean dirt & corrosion off the socket & freshen it up so that it should have good contact.
Boom
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Post by The Mad Norseman on Feb 16, 2014 13:58:57 GMT -5
The connection has become loose inside the plate amp on that RCA jack. If you can solder, pull out the plate amp and have a look. The socket's outside jacket should be firmly grounded, and the tip wiper & its connection should have a clean, shiny hot solder joint. If the soldered connection is dull or cracked looking, then either the factory had a "cold solder joint," or the connector has failed from mechanical stress over time. Occasionally, the tip wiper (that usually relies on the springiness of the steel connector to wipe the tip of the RCA plug) has just become fatigued and no longer makes as good a connection as it once did. Occasionally, you can bend that wiper back so that it has better tension, but often, you can't get to it at all. If necessary, you can buy a new (and probably better quality) jack from either Parts Express or Radio Shack & install it in place of the original. I wish I could give you better news, but from what you describe, it sure sounds like a mechanical problem with the jack. The sure telltale is that you can sometimes jiggle the connector & get it to work. Best of luck with it - If you lived nearby, I'd be happy to drop by & solder in a fresh jack for you, but that proximity isn't likely. You might also check to ensure that the "leaves" of the ground on the RCA plug are making good contact with the socket. You can have no sound from EITHER loss of ground OR loss of signal. Sometimes the leaves of the male plug (particularly if it's a cheap or fancy cable) can be either too flexible (cheap cable) or too rigid (fancy cable) to make good contact. If they don't make a firm contact with the input socket, then you get no sound. I've had to take a pair of pliers before & compress the outer leaves of the male RCA plug to make them hook up consistently. Also, if the input socket is not clean, you can get enough dirt/corrosion on it to prevent contact. The socket should be clean & shiny looking. If it isn't then go to Wal Mart or any hardware store & buy a can of "Nevr-Dull." A pinch of the cotton wadding will clean dirt & corrosion off the socket & freshen it up so that it should have good contact. Boom ^^^ Thanks Boomer! That's all good advice, and it sounds like you know what you're talking about too! (Not always the case with some other advice I've received!  ). A couple questions before I dive in though: 1) What's a "tip wiper"? 2) What are "leaves of the ground" (on the RCA plug)? BTW, the cable itself is a good quality, 18' long Blue Jeans (subwoofer) cable. Also, the male and female connectors all look clean enough, but the 'Nevr-Dull' is also a very good idea, and certainly wouldn't hurt. Thanks again! |
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Post by Gary Cook on Feb 16, 2014 14:53:08 GMT -5
I note that in the original post you say you eliminated the cable, I assume that means you tried another one?
The centre (active) pin tip on the male RCA plug makes a connection to the female RCA active via a wiper. Over time the wiper loses it's tension and contact is lost.
The outer (neutral/earth/ground) on the male RCA plug makes a connection to the female outer via a cylinder with slots in it. The ID of the male is smaller than the OD of the female with the slots opening to allow insertion. Over time the tension of the cylinder can be weakened (slots stay opened) and contact lost. This is especially noticeable on heavy cables that hang their weight on the RCA connector.
By dragging down on the male RCA plug you are either assisting in the contact of the internal or external connection, or perhaps both.
Fatigue failure of the female RCA is unusual, normally it's the male RCA that fails first, commonly at the wire to plug connection. Which is easily solved by swapping cables.
Cheers
Gary
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Post by Boomzilla on Feb 16, 2014 15:00:39 GMT -5
Mr. Cook got it right.
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Post by The Mad Norseman on Feb 16, 2014 22:05:16 GMT -5
I note that in the original post you say you eliminated the cable, I assume that means you tried another one? The centre (active) pin tip on the male RCA plug makes a connection to the female RCA active via a wiper. Over time the wiper loses it's tension and contact is lost. The outer (neutral/earth/ground) on the male RCA plug makes a connection to the female outer via a cylinder with slots in it. The ID of the male is smaller than the OD of the female with the slots opening to allow insertion. Over time the tension of the cylinder can be weakened (slots stay opened) and contact lost. This is especially noticeable on heavy cables that hang their weight on the RCA connector. By dragging down on the male RCA plug you are either assisting in the contact of the internal or external connection, or perhaps both. Cheers Gary Thanks Gary. I believe by exerting downward pressure on the cable where it connects that I'm 'assisting in the contact of the internal connection', at least that's sure what it seems like. Does that make a difference in how I approach this? Also you typed: "The centre (active) pin tip on the male RCA plug makes a connection to the female RCA active via a wiper. Over time the wiper loses it's tension and contact is lost".
I believe this is exactly what has happened, but how does a 'wiper lose its tension'? How can I re-establish a dependable 'inner' contact once its become tenuous? Maybe before I take this apart I should try and crimp the outer jacket of the male RCA plug for a tighter fit first and se if that makes a difference? Though the type I'm using doesn't look like there's room fro crimping as its a complete cylinder. I'm using Blue Jeans Cables Belden 1505F type subwoofer cables: www.bluejeanscable.com/store/subwoofer/index.htm |
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Post by Boomzilla on Feb 16, 2014 22:17:02 GMT -5
If you can feel tension as you push the make plug into the subwoofer's jack, then you should have a good ground connection. If the plug almost falls off, or feels like there's no tension at all when you connect the cable, then the cable's ground needs to get snugged up.
Once the internal wiper loses tension, there's not much you can do but replace the jack, in my experience.
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Post by Gary Cook on Feb 16, 2014 22:26:15 GMT -5
If you can feel tension as you push the make plug into the subwoofer's jack, then you should have a good ground connection. If the plug almost falls off, or feels like there's no tension at all when you connect the cable, then the cable's ground needs to get snugged up. Once the internal wiper loses tension, there's not much you can do but replace the jack, in my experience. Agreed. As it has no slots, you could try making the outer jacket of the male RCA a bit oval in shape. Cheers Gary |
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Post by The Mad Norseman on Feb 17, 2014 12:25:04 GMT -5
If you can feel tension as you push the make plug into the subwoofer's jack, then you should have a good ground connection. If the plug almost falls off, or feels like there's no tension at all when you connect the cable, then the cable's ground needs to get snugged up. Once the internal wiper loses tension, there's not much you can do but replace the jack, in my experience. I think the outer (ground) jacket has good tension, and seems to make full contact - its just when its pushed in all the way straight and tight it then seems like the inner 'pin' on the male cable is not making contact internally (If that makes sense?). But when I exert downward pressure on the subwoofer cable's exterior, it makes internal contact and passes the signal. It's probably what you said Boomer about the 'wiper' losing contact/(tension?) which will (eventually) require replacement of the RCA jack itself. Here's a photo of my 'jury-rigged' temporary fix...such that it is...  Attachment Deleted |
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Post by Boomzilla on Feb 17, 2014 12:35:12 GMT -5
If it works, it works!
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Post by Gary Cook on Feb 17, 2014 15:18:45 GMT -5
The old lacky band temp repair, been done many times. As long as the tension stays it will keep on working, a new lacky from time to time. Eventually you will have to replace the female RCA, not because it stops working, but it will play on your mind that's it's just not right. It will chew away at you subconsciously until you either fix it permanently or you go crazy. Hopefully the former.
Cheers
Gary
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Post by The Mad Norseman on Feb 17, 2014 17:13:07 GMT -5
The old lacky band temp repair, been done many times. As long as the tension stays it will keep on working, a new lacky from time to time. Eventually you will have to replace the female RCA, not because it stops working, but it will play on your mind that's it's just not right. It will chew away at you subconsciously until you either fix it permanently or you go crazy. Hopefully the former. Cheers Gary Gary, you're a mind reader! - its already bugging me even though this works!  I've contacted a local electronics repair outfit that says they can re-solder or replace the female RCA jack, so I've got that as my fallback position. But you're right that even if this 'fix' continued to work forever, it will 'chew away' at me as you so succinctly put it! At least this buys me some time where I can then do it when its convenient for me. I'll then open it up and see if its something I can replace or re-solder it myself first. If 'the wiper' has lost contact, is it pointless to re-solder it in then? Is replacement of the RCA jack then necessary? I'm not sure why it would be, because its really only just a metal conductor... |
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Post by Gary Cook on Feb 17, 2014 17:22:52 GMT -5
The old lacky band temp repair, been done many times. As long as the tension stays it will keep on working, a new lacky from time to time. Eventually you will have to replace the female RCA, not because it stops working, but it will play on your mind that's it's just not right. It will chew away at you subconsciously until you either fix it permanently or you go crazy. Hopefully the former. Cheers Gary Gary, you're a mind reader! - its already bugging me even though this works! I've contacted a local electronics repair outfit that says they can re-solder or replace the female RCA jack, so I've got that as my fallback position. But you're right that even if this 'fix' continued to work forever, it will 'chew away' at me as you so succinctly put it! At least this buys me some time where I can then do it when its convenient for me. I'll then open it up and see if its something I can replace or re-solder it myself first. If 'the wiper' has lost contact, is it pointless to re-solder it in then? Is replacement of the RCA jack then necessary? I'm not sure why it would be, because its really only just a metal conductor... I'm not a mind reader, I've just been there before. My suggestion would be to take the opportunity to replace the female RCA with one of higher quality. It's a common problem with RCA connections on subwoofers, the weight of the cable dragging down on the plug, plus the vibration wears out the lower quality connectors fairly quickly. Cheers Gary |
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Post by The Mad Norseman on Feb 18, 2014 13:27:26 GMT -5
Gary, you're a mind reader! - its already bugging me even though this works! Is replacement of the RCA jack then necessary? I'm not sure why it would be, because its really only just a metal conductor... I'm not a mind reader, I've just been there before. My suggestion would be to take the opportunity to replace the female RCA with one of higher quality. It's a common problem with RCA connections on subwoofers, the weight of the cable dragging down on the plug, plus the vibration wears out the lower quality connectors fairly quickly. Cheers Gary Someone over on the JBL thread at AVS suggested just switching the subwoofer cable input to the right/red RCA input. He says that when the subwoofer is switched to LFE mode (disabling the crossover control), that both the Left & Right RCAs behave the same way. But the manual makes a point of showing the connection to the LFE/Left RCA input when switched to LFE mode, and doesn't say that either input can be used. But maybe it can? And that's just a manual oversight? Hmmm... |
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Post by Keith M on Feb 18, 2014 13:41:17 GMT -5
I've run across other situations before where seemingly you could use either input, but the left always seems to be the one mentioned in the manual. As an example my SVS AS-EQ1 manual says to use the left or center input for level matching, but doesn't say to use the right. Maybe this is just a convention. If the manual says left, people will use the left input, but if it says use either people will be confused and call tech support.
Try it and see. Chances are good it'll work just fine.
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Post by The Mad Norseman on Jul 31, 2015 19:39:46 GMT -5
Just as a long overdue follow up to this old thread...
My temporary "fix" lasted far longer than I ever expected it to (see photo I posted in this thread above), and the connection finally became quirky - forcing me to do what I should have done initially.
Take 'er in to get 'er fixed!
No, not neutered or spayed, but to have that RCA jack that came loose internally professionally re-soldered, and everything put back as new.
Got 'er done a couple months ago, and everything works "as new" again now.
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