[Jason Kooner]

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

[chuck]

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.

[Mark Zacharias]

"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.

[Jason Kooner]

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.



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.




I have the manual now ...thanks. Also I did find some 0.22ohm half watt resistors that were open. There is also one BF469 NPN transistor that is bad but I can't find it online. I tried searching for recommended alternate but no one carries those either...too old.

Can I just lookup the Hfe, voltage and ft on the datasheet and search on mouser od digikey for the same specs? Or does anyone know of a BF496 sub that I can get in 2014?

thanks,

-jason

[chuck]

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.



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.




I have the manual now ...thanks. Also I did find some 0.22ohm half watt resistors that were open. There is also one BF469 NPN transistor that is bad but I can't find it online. I tried searching for recommended alternate but no one carries those either...too old.

Can I just lookup the Hfe, voltage and ft on the datasheet and search on mouser od digikey for the same specs? Or does anyone know of a BF496 sub that I can get in 2014?

thanks,

-jason


NTE108. Mouser Electronics or MCM may have it in stock.

[Jason Kooner]

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.







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.









I have the manual now ...thanks. Also I did find some 0.22ohm half watt resistors that were open. There is also one BF469 NPN transistor that is bad but I can't find it online. I tried searching for recommended alternate but no one carries those either...too old.



Can I just lookup the Hfe, voltage and ft on the datasheet and search on mouser od digikey for the same specs? Or does anyone know of a BF496 sub that I can get in 2014?



thanks,



-jason





NTE108. Mouser Electronics or MCM may have it in stock.


I replaced the bad components but it failed again. I think I missed a few 1K fusible resistors that are open. They connect to the gates of the power fets so I think the gate was floating on 2 fets when I fired it up.

I'll replace all the bad parts again but this time I'll bring it up slowly at my work since I have better equipment there.

I do have 2 questions:

1. On page 32/35 of the schematic there is a 2K pot in the near the middle of the page. I assuming this is used to adjust the bias of the power stage to some level. I have a function generator to help with this, where should I place my scope probes when adjusting this pot and what am I looking for?

http://elektrotanya.com/infinity_ove.../download.html


2. On the same page there is a 1K 2W (R68) resistor on one of the relay contacts, what is this for?

thanks,

-jason

[[email protected]]

I have the same speakers with same problem. How do you get to the amp? Get them open?