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.
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