The front panel logo of Neumann KH310 is always red

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winner

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Sep 19, 2017
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I have two KH310, one of which has normal sound and function, but the panel light is always red. After using another circuit board for troubleshooting, I came to the conclusion that its main board (the back of the speaker) is faulty. After troubleshooting, it was found that the LED lights are controlled by the comparator lm339/393. I replaced them, but the problem still persists because its circuit board is multi-layered and I cannot see the wiring inside. Therefore, I am seeking help, Has anyone encountered this situation before?

The following are photos of the circuit board. I hope someone can help. Thank you
Main1.jpg
 
Why not ask Neumann? They would be the ones that know..
I have contacted them and they have expressed that they cannot support it and can only replace the motherboard for me at a price of $480. I think this is just a small issue and it is not worth it
 
What does the logo being red indicate?

According to the manual if the logo is solid red means that there is a temperature issue. That the temp is too high. It should then reduce output by 20dB
 
@winner Have you sorted out the issue? I have a similar issue on one of my 2 KH310: the speaker sounds ok, but the led remains off and very seldom (it happened like a pair of times in months of use), lights up in a fuzzy way like if it there was some sort of dirty contact and returns to life working normally for say one hour or two, and then turns back off again. Also in my case however, it's very unlikely that the problem is caused by a dirty contact, because I have tried everything including opening the speaker and disconnect-reconnect the led wire, but nothing seems to work. I guess that either the comparator that you mentioned or a component around it (perhaps a transistor, judging by the fuzzy behavior of the led in the rare cases in which it returned to life) must has gone bad... I haven't tried contacting Neumann but if they want almost 500 euro because they would change the entire main board, I'm with you and I'm not gonna pay them so much only for having the led working again. Not to mention the hassle of having to send the speaker who knows where and wait for it to be serviced.
 
@winner Have you sorted out the issue? I have a similar issue on one of my 2 KH310: the speaker sounds ok, but the led remains off and very seldom (it happened like a pair of times in months of use), lights up in a fuzzy way like if it there was some sort of dirty contact and returns to life working normally for say one hour or two, and then turns back off again. Also in my case however, it's very unlikely that the problem is caused by a dirty contact, because I have tried everything including opening the speaker and disconnect-reconnect the led wire, but nothing seems to work. I guess that either the comparator that you mentioned or a component around it (perhaps a transistor, judging by the fuzzy behavior of the led in the rare cases in which it returned to life) must has gone bad... I haven't tried contacting Neumann but if they want almost 500 euro because they would change the entire main board, I'm with you and I'm not gonna pay them so much only for having the led working again. Not to mention the hassle of having to send the speaker who knows where and wait for it to be serviced.
same here. the LED/bulb on my left KH 310 started working bad few days ago, and now has definetly died. The speaker runs fine at the moment. I just wanted to know if it was possible to have one and service it here by myself (I think warranty has expired, I don't know if I have a total of 2 or 3 years of warranty). Neumann support just said "you can't repair by yourself" and gave me a link of the company who is in charge of servicing this product in Italy. Of course I won't stay without a speaker for a light/led.

and by the way... we are pretty close, I am based in Piove di Sacco/Campolongo Maggiore :)
 
update: neumann told me who is responsible in italy. this 2nd company told me who is reponsible for spare parts and repair in my region. this 3rd company told me that the single led is not replaceable, and they (not me) should replace the entire board (!). of course I won't do that. in my case my led is very very lightly lit, indipendently of the position it is set to. the overload red led works fine. if I really need to, I'll open it and check if there something I can do by myself, maybe it's just a feed/link/contact problem. cheers, Alessandro
 
Mine is always orange(!), never white, never red, and works flawlessly. So I never bothered to get it repaired. : ) I remember I wrote to their customer service, we had a couple of conversation, but then conversation died. Apart from the fact that these are awesome monitors with incredible sound, the board must be very "skibidi" in terms of LED illumination and probably they are aware of it. And it's very busy too, SMDs everywhere... that on the top on the first photo doesn't look good.
As far as I remember the LED has its own small board behind the logo, have you checked that first? The Neumann CS said that they could send two to check if it helps, but this never happened. If you have mood and skillset, maybe check that too. Two screws holds it in place, it is like 2x2cm board or so. Or just switch lights off and that's it. I'm already getting take up with the idea that my speakers will be illuminated with orange color for ever and ever, at least it's symmetrical, and nicer than cold white.
 
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update: neumann told me who is responsible in italy. this 2nd company told me who is reponsible for spare parts and repair in my region. this 3rd company told me that the single led is not replaceable, and they (not me) should replace the entire board (!). of course I won't do that. in my case my led is very very lightly lit, indipendently of the position it is set to. the overload red led works fine. if I really need to, I'll open it and check if there something I can do by myself, maybe it's just a feed/link/contact problem. cheers, Alessandro
Hi Alessandro, nice to read that we live so close, I am in Mestre in fact! I tried opening the speaker a second time, only to come to the conclusion that It's better to leave it as it is, because it's definitely an issue located on the main board, and for sure it's not worth replacing the entire board at the cost of hundreds euro just for it. Attempting a repair without a schematic on such a dense multilayer board is also too risky for me, as I wouldn't want to end up damaging also something in the audio path.
So in the end, I switched off also the LED on the other speaker to make them look "symmetrical" (LOL) and decided to stop bothering about it.
Ciao, and Happy New Year to everybody!
 

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