I'll check what variant it is when I see it later.
Yes DO NOT buy on UK ebay, you might as well take it for granted that they are all fakes or ESD damaged because most ebayer's don't care or know about that.
4227's are especially difficult to get at the moment, I've had to wait months on back order sometimes in the last few years... 🙁
Not a good idea to use ebay semi conductors if you want reliable repairs... 😳
My tester is the one called the "AY-AT" version with red motherboard, loads of details in the transistor tester hyperthread at eevblog forum. Bought it as cheap kit and upgraded to more precision parts for better accuracy... MOD part list and details available on same thread at eevblog... 🙂
Thanks for all the answers! I ordered a new solder sucker cos I have been struggling with desolder the FETs with my current one (especially source pin). Any good tips and trix for that btw? I will try the method suggested then. 🙂
Attached file will help with matching fets.
For de-soldering, it's probably lead free solder that is on the board so add some leaded solder to the joints before using the sucker, this will make the joints melt at a lower temperature and much easier to work.
You can also "walk" the 3 legs out of the board by heating two pins till solder melts then lifting the component a tiny bit on that side and holding till the solder sets, then do the same for the other side and repeat the process till the component is worked free, then clean holes with solder sucker.
With some iron tips you can heat all 3 pins at the same time and lift out.
Always add some leaded solder first to make things easier... 🙂
For de-soldering, it's probably lead free solder that is on the board so add some leaded solder to the joints before using the sucker, this will make the joints melt at a lower temperature and much easier to work.
You can also "walk" the 3 legs out of the board by heating two pins till solder melts then lifting the component a tiny bit on that side and holding till the solder sets, then do the same for the other side and repeat the process till the component is worked free, then clean holes with solder sucker.
With some iron tips you can heat all 3 pins at the same time and lift out.
Always add some leaded solder first to make things easier... 🙂
SO.... I finally got around and tested this. I swapped the FETs from channel A to channel B and Voila! Channel B works without problems. Then I went ahead and put one of the original FETs in one channel each accompanied with a new one but that didn't work, started to overheat again.
It's seems to be obvious that the new FETs are incompatible with the old ones so what now? Where do I go from here?
It's seems to be obvious that the new FETs are incompatible with the old ones so what now? Where do I go from here?
So it's obvious that it's just the FETs that are the problem but I'm not sure how to tell you to proceed as I think you only have a multimeter... or do you have more test equipment?
No unfortunately not. What is the cheapest thing I need to be able to test it further? I don't really have budget now to fit a spontaneously scope purchase even though I really should get/invest in one.
The objective is to test the characteristics of the FETs that are staying cool and find suitable matching replacements for the other channel...
or adjust the gate resistors for the FETs that are getting hot but you would need a scope for that I think...
I'm really busy at the moment doing something completely different ... Let me think about this and I'll get back to you when I have time.
If anybody else has a more immediate solution or suggestion for Thridel right now please feel free to chime in...
or adjust the gate resistors for the FETs that are getting hot but you would need a scope for that I think...
I'm really busy at the moment doing something completely different ... Let me think about this and I'll get back to you when I have time.
If anybody else has a more immediate solution or suggestion for Thridel right now please feel free to chime in...
Ok I understand, no problems. You have been really helpful so far and I really appreciate it. Good luck with your project!
I still haven't solved this.
Is there someone who have any ideas of how i can get a hold on correct FETs that matches my original ones?
Other suggestions?
Thank you!
Is there someone who have any ideas of how i can get a hold on correct FETs that matches my original ones?
Other suggestions?
Thank you!
https://octopart.com/irfb4227pbf-infineon-65873827
Order from a known, trusted distributor in your region. It may be worthwhile to order a whole new set so their characteristics are similar.
Order from a known, trusted distributor in your region. It may be worthwhile to order a whole new set so their characteristics are similar.
I agree with von above.. the FETs are more easily available now.
With the lack of equipment you have this is the only option. If you want to test the working fets from the other channel and try to match parameter for the original gate resistors I have already sent you the simplest way to do that above (with any 12 or 15v psu, a single resistor and a multimeter).
There is no other "off the shelf" solution for your lack of knowledge & test equipment...
What would help is for you to use the super simple FET test setup and post the measured parameter here for others to see.
There is nothing further that the forum can do without parameter info...
With the lack of equipment you have this is the only option. If you want to test the working fets from the other channel and try to match parameter for the original gate resistors I have already sent you the simplest way to do that above (with any 12 or 15v psu, a single resistor and a multimeter).
There is no other "off the shelf" solution for your lack of knowledge & test equipment...
What would help is for you to use the super simple FET test setup and post the measured parameter here for others to see.
There is nothing further that the forum can do without parameter info...
Thank you check12 and von Ah, I´ll test new FETs once again now that they are in stock everywhere.
I meant test the FETs that work, then the FETs that overheat with the simple test setup detailed in the attachment in post #44 to see the difference... 🙂
D
Deleted member 148505
If this is the correct NX3000 schematic (from web), you can increase the deadtime if you are ok with it, to avoid heating fets.
Remove 8K2 resistor to set it to DT4 (45ns) or replace the gate resistors to 6.8 ohms.
If the fets are genuine to begin with, you don't need to match them to the fets that are currently installed.
Also, check the oscillating frequency, if it changed, you need to set it to the original operating frequency. If you don't have a scope to check for frequency, you can check it with a multimeter or frequency counter (probe after the output inductor / speaker out)
He already tried the FETs from the other channel on the channel to be repaired & they worked fine (as expected)... the simple "matching" test circuit attached above was the simplest way to just see the difference in the new FETs (that he thought were genuine) with only his multimeter to help understand why they are overheating.
I did not say they had to match the other channel meaning that as a point of principal... it was just because the FETs from the other channel were proven to work... 🙂
IMO it would be much easier to buy definitely genuine fets from a major supplier and see if the Vgs parameters matched the proven working FETs... than to start trying to adjust dead time & gate resistors for the mystery "hot" FETs with only a multimeter.
Both ways will work though... 🙂
D
Deleted member 148505
Buying genuine would definitely solve the problem, although I've noticed that there are 2 people complaining about the same failure, that's why I think increasing the deadtime would be a good way to increase the reliability. Either the amp was designed with tight tolerances to achieve something, or designed for planned obsolescence, in such a way that it will break at a slight drift in MOSFET parameters. Removing 2 resistors for DT settign will do it (changing the gate resistors is risky for one with only a multimeter). I don't think it will drastically change the performance of the amp, provided that he uses genuine FETS, that's why I emphasized the importance of getting genuine parts..
Agreed.... It's Behringer so planned obsolescence will be the motive. Yes definitely genuine FETs... increasing deadtime sounds like a good idea to try and it's an easy mod for him.
I'm interested to see the outcome.
@Thridel ... Make sure and use good NON CONDUCTIVE heatsink compound... I saw a powered speaker recently that had shorted through cheap compound that was supposed to insulate to 10kV but obviously didn't..
I've been using arctic silver "Ceramique 2" ... It's good and if you shop about can be found cheap... If it's just for this repair the small syringe size will be plenty and will also help to keep temps down... 👍
I'm interested to see the outcome.
@Thridel ... Make sure and use good NON CONDUCTIVE heatsink compound... I saw a powered speaker recently that had shorted through cheap compound that was supposed to insulate to 10kV but obviously didn't..
I've been using arctic silver "Ceramique 2" ... It's good and if you shop about can be found cheap... If it's just for this repair the small syringe size will be plenty and will also help to keep temps down... 👍
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