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#1
Posted to rec.audio.tech
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infinity overture 2 repair
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. |
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#2
Posted to rec.audio.tech
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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. |
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#3
Posted to rec.audio.tech
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infinity overture 2 repair
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 |
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#4
Posted to rec.audio.tech
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infinity overture 2 repair
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. |
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#5
Posted to rec.audio.tech
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infinity overture 2 repair
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 |
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#6
Posted to rec.audio.tech
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infinity overture 2 repair
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. 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 I would replace all transistors Q 8 to Q 16. Make sure none of the fused resistors are open. Check all zeners for leakage and shorts. Also D11. Put a 60 to 100 watt light bulb in series with the hot side of the AC input and, once the light bulb dims and the relay closes, plug the amp directly into the wall and measure bias across one of the ..22 ohm resistors on the output fets. (Infinity specifies R77) Adjust for 5.9 mv after running the amp for 15 minutes. The pot is a bias pot. The R68 resistor appears to drain off the offset voltage when the amp powers down. This design is at least 30 years old so there shouldn't be any issues that Mark Z or I haven't seen before. |
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#7
Posted to rec.audio.tech
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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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