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What is wrong with subwoofer line filter circuit board?

Posted on 2008-06-22
Medium Priority
Last Modified: 2013-09-25
I have a Klipsch 10" Subwoofer with a built in line filter on the signal.  When powered on and fed a signal I get nothing.  I've tested feeding the unit multiple signls with no results.  Directly giving the speaker a low HZ signal confirms to me that the speaker is not the issue.  I don't see any capacitors that look buldging or any resistors that looked cracked.  There is a transformer looking piece that i believe has leaked and could be the problem.  I have a multimeter, but don't know how to test that compoenet.  I also don't how to determine what that component is, but i would think i could find a replacemnt part at mouser.com  Can anyone help solve this?

Board Details - BASH - INDIGO CANADA  600134 REV:2
Question by:shawnkimble
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Expert Comment

ID: 21841020
We'll probably need more information/background.  When did the unit stop working?  Can you think of anything significant such as a brown out condition or power fluctuation/spike that led up to the speaker failure?

I am assuming the unit is no longer under warranty.  If it is, I would strongly recommend contacting their warranty department.   Based on the pictures and information listed, I'm not seeing anything that may be the cause.  I would look closely for any scorched connections/components.  If you have a multimeter/continuity tester, check for continuity between the plug and AFTER the fuse/circuitbreaker (it looks like the fuse/CB is the round item right above the plug.

Author Comment

ID: 21841230
I have no idea when it stopped working, I don't use it a lot.  I've checked the fuse, the fuse is fine so I don't think it has a power spike issue.   Its older than 2 years, so warrantee doesn't apply, and I don't want to waste $ on shipping such a heavy object back when I know I can solve it myself.

Before I noticed when plugged in the speaker makes a click every so often when no signal is attached, but currently I'm unable to reproduce that.  This made me think it was a capacitory discharging, but again it doesn't seem to be doing that now.

Can you properly test the capacitors when they are on the board?  

Author Comment

ID: 21842321
I've also tested the following items on the board:

Top of Board 1
 - Input AC power at the point of entry on the board is 119V AC

Top of Board 2
 - 470uF 200 WV Center CAP with power on measures 162V DC, and power off 485 uF
 - 470uF 100WV Right CAP with power on measures 109V DC, and power off 400 uF  - This seems to operate out of tolerance, but i don't know if that really matters.
 - There is no continuity between speaker outputs
 - There is no continuity between either speaker output and either speaker input (Center of RC Jack) - Both while on or off

Bottom of Board
  - The outer jacket of the L& R RC Jack go to ground, and that appears to be the design of the circuit.

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Accepted Solution

danengle earned 1000 total points
ID: 21877048
Getting a bit beyond what can be diagnosed online.  I would try looking for any scorched  or failed components (which is appears you have).  The next best thing is to take it to a local TV/appliance repair shop.  call for a diagnosis quote first.  they could charge an arm and a leg up-front or some places go by hourly rate.
LVL 69

Expert Comment

ID: 24904047
You can diagnose capacitors using an ESR meter http://www.anatekcorp.com/testequipment/esrcompar.htm. Some capacitors can be tested onboard, but others have to be isolated.

Author Comment

ID: 24904710
I think I'll just replace the large Caps and see what happens.  I'll post an update if that solves the issue.
LVL 69

Expert Comment

ID: 24907901
If you do, try to use higher-temperature capacitors, as they are succeptible to drying out if they are in a hot location.  For example, there were 85C capacitors in a projector that eventually failed due to heat, and it was recommended to replace them with 105C models.

Expert Comment

ID: 25317433
I have the exact same unit. Mine works but the output is very low and very distorted.  The speaker works fine on another amp.  Need schematics very badly.   Please help :)

Author Closing Comment

ID: 31469533

Expert Comment

ID: 39513962
Try checking the MOSFETs on the large aluminum heatsink board. I believe one in voltage control and others are power amp. This is a current sensing amp.

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