Behringer NX3000D repair

[Rick2024]

Hey so I’m doing my 1st D class amplifier repair i purchased a Behringer NX3000D off eBay as faulty “dead on arrival” I spoke to the owner looks like he purchased a few of them and kept this one as a backup never used it he went to use it years later and one channel was in protect other channel made a bang sound though the speaker every time he turned it on he apparently did it a few times and now both channels are in protect I received the amplifier have not turned it on had a look couldn’t see any blown components I checked the Fets one fet is shorted across Gate drain and source rest of the fets read 5v on diode mode on my multimeter I tested every transistor resistor capacitor and diode after the drive IC chip on channel A & B and looks good a couple caps read a little high but ok i purchased new IRFB4227PBF and IRS20957STRPBF just incase I’ll replace the fets and the driver IC’s do you guys think it’s just a bad IRFB4227PBF I also had a Quick Look at the components in the power supply section and I think the power supply is ok looked at the diodes resistors and capacitors and couldn’t find anything I don’t want to risk turning it on and causing more damage am I on the right track hopefully it’s just the fet but I’ll replace all 4 fets and the 2 drive IC’s anyway

Cheers Ricky

[wasedadoc]

Are you hoarding full-stops to sell at a premium price during a future world shortage of them?  Or is your keyboard faulty?

[darkspr1te]

Behringer devices are well known for having dry joints, i've been in audio for 20 years now and all but one device has failed at some point due to that issue. So i would first go over the board and wobble caps and parts , I've seen the relays have issue also due to shock (carrying by the front handles and putting down hard often).


I would use the filament light bulb inline with mains power to act as a test light (if it lights you have a short)


There is a video here on repair and testing

and schematic here
https://music-electronics-forum.com/filedata/fetch?id=971304


darkspr1te
...............

[Rick2024]

Thank you I’ll pull the board out fully when I get the mosfets and ic drivers and have a look at the joints
Thank you @darkspr1te i already got a nx3000 service manual

 I don’t think it was damaged due to shock because it wasn’t used it was kept in the box as a new spare till he’s other one failed and when he opened new in box amplifier one channel wasn’t working and other channel made a bang noise though the speaker every time he turned it on and after a few times turning it on both channels went in to protect the mains fuse never poped but the only item I see thats faulty is mosfet #4 I’ll definitely check everything again to made sure there’s no other damage parts

Cheers Ricky

[Rick2024]

Looking to get a cheap lCR meter I was looking at the holdpeak HP-4070L / YF-4070L or the Mastech
MS8911 I want to troubleshoot this PCB further also some other PCB’s in the future I have a small budget do you guys recommend any of these if not what do you recommend for $100 AUD or under would like to test components in circuit

Cheers

[Rick2024]

I fixed the amplifier took me a while I replaced both pwm IC’s and I replaced the 4 mosfets and now it works so happy now I have a decent amplifier which cost me $140ish inc shipping and parts cost $70inc express shipping it’s brand new was DOA it’s worth about $900 aud luckily I found a good deal and saved my self a bit instead of buying new witch I wouldn’t afford new one

Thank you all for you help

Cheers Rick

[Rick2024]

Would I need to adjust the bias I replaced the mosfets for the exactly the same ones as the original mosfets the only difference being is that they would be a different batch number i turned the amplifier on it works but idk if i need to adjust the bias and if I do how do i do that