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Mark Zacharias Mark Zacharias is offline
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Default infinity overture 2 repair

"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.

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



Check for open resistors and open drive transistors.



UGH. Had to work on one of these once. Reminded me of a car amp.
Don't forget to use an isolation transformer.

The manual can be downloaded from Elektrotanya or you can email me at:



and reverse "labolgcbs" to read "sbcglobal".

They do get a number of open resistors. I my case, a predriver looked good
but wasn't. Caused additional heartache. Got it working, but it wasn't worth
the trouble for me. If business hadn't been slow I would have just turned it
away.

Mark Z.