The front panel logo of Neumann KH310 is always red

[winner]

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

 

[gyraf]

Why not ask Neumann? They would be the ones that know..

 

[winner]

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

 

[pucho812]

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

 

[onununo]

@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.