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Jason Kooner Jason Kooner is offline
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Default infinity overture 2 repair

On Monday, April 7, 2014 9:55:19 AM UTC-5, chuck wrote:
On Sun, 6 Apr 2014 20:59:26 -0700 (PDT), Jason Kooner

wrote:



On Monday, March 31, 2014 3:19:13 PM UTC-5, chuck wrote:


On Mon, 31 Mar 2014 10:19:55 -0700 (PDT), Jason Kooner




wrote:








On Sunday, March 30, 2014 1:37:06 PM UTC-5, Mark Zacharias wrote:




"chuck" wrote in message








...








On Thu, 27 Mar 2014 21:23:14 -0700 (PDT), Jason Kooner








wrote:
















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.