Behringer Eurolive B812NEO cutting in and out repair

[CapLeaker]

Got this Behringer Eurolive B812NEO in for repair.

Complaint: It keeps cutting in and out all the time.

After opening the speaker, I saw a little spark on the AC input. Aaand? The porblem is a broken thermistor leg (R53) SCK252R0. Fixed it and she is rolling again. Same Decon caps crap in this Behringer unit.

The schematic is for a B912NEO, but it's close enough for this one.

[petehall347]

Re: Behringer Eurolive B812NEO cutting in and out repair

well done .. not got round to looking at Behringer broken ones i have been gifted yet . at least 2 mixers that i remember ..

[CapLeaker]

Re: Behringer Eurolive B812NEO cutting in and out repair

I just fixed an older Peavey powered speaker that was clipping, low volume and the heatsink got hot. The output was shorted to GND. Right now I just finished the to-do pile.

A little note to that B812NEO. There are actually two thermistors in series. Got me a bit head scratching in why one would do that?

[petehall347]

Re: Behringer Eurolive B812NEO cutting in and out repair

weakest link .

[CapLeaker]

Re: Behringer Eurolive B812NEO cutting in and out repair

Yeah... usually one thermistor or one resistor as inrush current limiter. But why 2 in series? Specifically those dumb SCK252R0 that's hard to find with power ratings like that.

[momaka]

Re: Behringer Eurolive B812NEO cutting in and out repair

A little note to that B812NEO. There are actually two thermistors in series. Got me a bit head scratching in why one would do that?

I'm not 100% sure, but if I had to guess, they probably did this to get a higher "cold" resistance - i.e. less inrush current at cold startup.

Now the real question is: does the circuit really need/benefit from using the two series thermistors, or can you just cram in something bigger with higher current spec and lower cold/On resistance without compromising the rest of the circuit?

*EDIT*
I see the input bulk filter/storage caps for the PSU in this amp are 2x 200/250V 2200 uF in series. That's quite a bit of capacitance there, so the inrush current would indeed be very high. What they should have really done with the design is use a 5 Watt or 10 Watt resistor in place of the two thermistors, and a relay coil to bypass it once the caps charge to a certain level. Of course, this would NOT have been the cheaper option, so I can imagine why Behringer didn't do it.

Same Decon caps crap in this Behringer unit.

Yeah, I got an EPQ 1200 amp unit in the closet with those craps. They are still okay and the amp is working. But who knows for how long.

Then again, what can you expect when you see something is "Designed" in Germany but Made in China?