Klipsh promedia 2.1 subwoofer amp broken - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th February 2008, 01:59 PM   #1
Dethoff is offline Dethoff  United States
diyAudio Member
 
Join Date: Feb 2008
Default Klipsh promedia 2.1 subwoofer amp broken

A few years ago I purchased the Klipsh Promedia 2.1 speaker system for use with my computer. All worked great until two days ago when I noticed a loud hum emanating from the sub woofer.

I did some trouble shooting which determined the following:

1. The humming is noticed as soon as the power is turned on. It does not change in volume as the volume control for the sats or sub are increased/ decreased.

2. I have tried plugging it into other outlets, which did not help.

3. The hum is there even if the audio input cable is disconnected or connected to another source (tried an mp3 player)

4. The sats seem to work fine.

5. The sub does not seem to work correctly. It seems to put out too low a volume and the sound from it seems distorted.

6. After taking the sub apart, I verified that the hum comes from the speaker (as opposed to an electonic part). The four largest radial electrolytic capacitors on the one board have a brown "gook" around them which I think is an indicator that they have failed and leaked. They are both rated at 4700 uf. One is 63 v, the other 35 v.

Does it make sense that it would be the caps? I would try my hand at replacing them, but after searching radioshack and the net, I can't seem to find capacitors of the same value.

Any advice would be appreciated.

Thanks,

John
  Reply With Quote
Old 10th February 2008, 02:01 PM   #2
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
Try resoldering the caps.

/Hugo
  Reply With Quote
Old 10th February 2008, 02:17 PM   #3
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
I'd say either the caps have failed or the (probably pathetic bridged car-amp chip) amplifier has failed. The brown gook is probably adhesive that holds the capacitors to the board for mechanical stability. If they had failed, the tops would be domed or ruptured.

Take some pictures
  Reply With Quote
Old 10th February 2008, 03:25 PM   #4
Dethoff is offline Dethoff  United States
diyAudio Member
 
Join Date: Feb 2008
I disassembled the electronics so I could get at the boards in question. Upon closer inspection, I do NOT think the "gook" is leaked capacitor electrolyte, but rather adhesive placed there. The caps are not deformed in the sense of bulges or cracks.

With the board out, I can now see another potential problem. The circuit board itself is a brown color, like butterscotch. But, at one place, the board has a really dark brown charred appearance, which I interpret to be a sign of extreme heat exposure. In the vicinity of this discoloration are two resistors which seem cracked and disintegrating.

I will try to take some pictures and post them.

Thanks
  Reply With Quote
Old 10th February 2008, 03:39 PM   #5
Dethoff is offline Dethoff  United States
diyAudio Member
 
Join Date: Feb 2008
here is a picture of the caps in question
Attached Images
File Type: jpg caps.jpg (81.6 KB, 189 views)
  Reply With Quote
Old 10th February 2008, 03:49 PM   #6
Dethoff is offline Dethoff  United States
diyAudio Member
 
Join Date: Feb 2008
Here is a picture of the heat damaged area and resistors in question.
Attached Images
File Type: jpg bad resistor.jpg (73.9 KB, 192 views)
  Reply With Quote
Old 10th February 2008, 05:58 PM   #7
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
Ouch...it looks like there's a little more work to do.
I'd start with measuring the resistors (if still possible) and replace those. A plain resoldering of the board, especially the places that suffered from heat, could solve the problem.
If not, jaycee's tip on the chip might be correct.

/Hugo
  Reply With Quote
Old 10th February 2008, 06:12 PM   #8
Dethoff is offline Dethoff  United States
diyAudio Member
 
Join Date: Feb 2008
I tried checking the resistors with a multimeter, but I am unable to read the color codes due to the charring. I do not have acess to a schematic, but am inquiring about the resistors values on the Klipsch forum.

If it is just a matter of checking the resistors value and repalacing them, I would be up to the task. Beyond that, I might be over my head.

Thanks
  Reply With Quote
Old 10th February 2008, 11:51 PM   #9
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
What's on the TO-220 packaged transistors at the edge of the board?

To be honest, the whole board is badly discoloured. You probably have more parts bad there.

Is that a transformer at the top left of the picture?
  Reply With Quote
Old 11th February 2008, 12:06 AM   #10
TheMG is offline TheMG  Canada
diyAudio Member
 
Join Date: Jan 2008
I think there's more wrong than just the resistors. Resistors don't end up looking like that over time even if they run pretty hot.

If I had to guess, I'd say one or both of those transistors or another part of the amplifier failed and shorted out internally, which would cause the resistors to burn up like that.

There's also a chance that the amplifier failure may have cause damage to the subwoofer driver too if there isn't any DC protection and the amplifier became railed after failure.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need help with Klipsch 2.1 Promedia Please mrfix90 Subwoofers 0 31st March 2009 03:45 AM
Mortified ProMedia sub tenzip Subwoofers 6 24th January 2007 01:46 AM
Klipsh Horns croat47 Swap Meet 1 7th December 2006 03:16 AM
bass section horn klipsh la scala jbsteeple Multi-Way 2 31st July 2006 05:28 PM
Fixing possible broken subwoofer Sepultura Subwoofers 11 25th August 2004 07:24 AM


New To Site? Need Help?

All times are GMT. The time now is 11:34 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2