Krk V6 s2 buzz

[blags]

Hello,
I own these monitors and they buzz without anything connected to them. I opened them the other day and there is no trace of black goo that made problem to rokit series the pcb looks like new. None of caps are bulged, everything seems to be ok. Since I know how to solder but have no experience in tracing the problem can someone point me what capacitor or component may be faulty. I contaced customer support but got no answer. Only existing schematics is the one for the larger, V8, model of this monitor. In attachment is a schematics.

Thanks in advance

[janoc]

That could buzz for millions of reasons.

Short the inputs - does it still buzz like that? If it doesn't, it is probably just picking up noise "from the air".

[blags]

To short + and cold on xlr input?

[janoc]

Yes. However, keep in mind that that amplifier has balanced input, so you may have to connect all three inputs pins together, not only two.

Good amplifier will be silent if you do that, at best you may hear a bit of noise/static when you turn the volume up.

If it still buzzes, then the question is what kind of buzz are you hearing - regular 50/60Hz mains hum? Or something else? If it is mains hum, I would measure the power supply capacitors, they could be dried out (they don't have to be bulging to be bad!).

If it is not mains hum then the problem is more complex and you will need to trace the circuit out by comparing it to the schematic and try to isolate which part is causing the noise - e.g. by breaking the connections between the stages one by one and seeing when it stops doing it. Then you have the stage which has a problem and you will need to debug it in order to identify the issue - could be all sorts of things, bad capacitors, broken resistor, broken solder joint, amplifier oscillating for some reason, power supply problem making something oscillate, ...

However, if you don't have at least a multimeter (oscilloscope would be useful too but not absolutely necessary) and some experience it would be better to find someone more knowledgeable who could help you. It is not really that complex, this speaker is a fairly simple device, but one still needs to know at least the basics of how it works, what to look for and how to use the available tools to troubleshoot it. And that is not something someone can teach you over a forum like this.

[KhronX]

With a differential amp on the input, wouldn't "just" shorting the two signal inputs together (pins 2-3 on an XLR) suffice?

Yes. However, keep in mind that that amplifier has balanced input, so you may have to connect all three inputs pins together, not only two.

[janoc]

With a differential amp on the input, wouldn't "just" shorting the two signal inputs together (pins 2-3 on an XLR) suffice?

Yes. However, keep in mind that that amplifier has balanced input, so you may have to connect all three inputs pins together, not only two.

In theory yes but it is simpler to short all three, especially if you aren't sure about the pinout.

[KhronX]

You say that, but all the XLR connectors i've seen, if memory serves, have the pins (or sockets) actually numbered, plus the pinout's quite standardized (1 = ground/shield, 2 = "hot", 3 = "cold").

https://en.wikipedia.org/wiki/Balanced_audio#Connectors

With a differential amp on the input, wouldn't "just" shorting the two signal inputs together (pins 2-3 on an XLR) suffice?

Yes. However, keep in mind that that amplifier has balanced input, so you may have to connect all three inputs pins together, not only two.

In theory yes but it is simpler to short all three, especially if you aren't sure about the pinout.

[janoc]

You say that, but all the XLR connectors i've seen, if memory serves, have the pins (or sockets) actually numbered, plus the pinout's quite standardized (1 = ground/shield, 2 = "hot", 3 = "cold").

https://en.wikipedia.org/wiki/Balanced_audio#Connectors

Of course but don't forget that the OP isn't skilled in electronics. It is simpler to tell him or her to tie all the pins together than having to explain which pin is which and which pins need to be shorted together.