From: jjkooner@gmail.com   
      
   Hello,   
      
   I have a pair of infinity overture 2 speakers. They have an internal amp to   
   power the woofer section. However, I don't here anything from the woofer.   
   There is a midrange and tweeter that are not powered and they work fine.   
      
   I unplugged one of the speakers and opened it up. There is some black dust on   
   the pcb near the power fets. There are 4 fets and they are all shorted. The   
   fets are Fairchild IRFS250B. I couldn't find these (too old) so I replaced   
   them with ST Micro    
   STW40NF20 fets. Also the power fets are grouped in 2 pairs with one pair   
   having an NPN transistor between them, why doesn't the other power mosfet pair   
   have this NPN transistor? The NPN is a Fairchild 2012, it measures ok with a   
   meter but I went ahead    
   and replaced it anyway.   
      
   I plugged in the speaker and tested it. The woofer is alive now but sounds   
   terrible, it's all distorted. The midrange and tweeter are fine.   
      
   I plan to bring a scope and thermal camera home from work for the weekend to   
   take some more measurements.   
      
   Questions:   
      
   1. Was that wrong to sub in the ST Micro fets? I did a datasheet comparsion   
   and didn't see anything special about the Fairchild fet.   
      
   2. Does anyone have a schematic for this pcb?    
      
   3. What other parts should I look at?   
      
   I think I was too quick to clean the black dust and should off spent some more   
   time trying to figure out the source!   
      
   Cheers!   
      
   -jason   
      
   --- SoupGate-Win32 v1.05   
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