Neumann KH120 studio monitor power supply repair

[MattLuie]

I repaired many power supply in the KH120 the problem was the four 220uF25Vdc capacitor around the two regulator in the output, psu, if the primary can start you can try that, I worked for Sennheiser-Neuman for a long time, good luck

I really appreciate you for sharing your experience here it definitely helps us
Thanks again

 

[MattLuie]

Hi again Folks
I'm here to report new updates
Last night I received new MOSFET which is 11N80C3 by infineon and I replaced it
But this time MOSFET didn't short very fast it shorted after 1 or 1and half min...
Really I'm going crazy this device isn't repair friendly guy's
Does anyone knows what value is the diode after this optocoupler that I attached down here
The diode was damaged I replaced with new 4148 MiniMelf I guess I made a mistake......
Best regards

 

[MattLuie]

I repaired many power supply in the KH120 the problem was the four 220uF25Vdc capacitor around the two regulator in the output, psu, if the primary can start you can try that, I worked for Sennheiser-Neuman for a long time, good luck

Sorry for asking but do you have any schematic of Neumann speakers????
I really need it to understand what's going on with these speakers....

 

[Narwhal]

Just in case anyone wonders across this and has the same issue as me (No blown fuse but power looping, LED swelling on and off and beeping sound).. I eventually got my broken one working again by replacing both amps (TDA7293) and this diode (30BQ100). I had a bunch of problems, most probably caused by myself, but eventually this is what worked out. Those amp chips are fiddly.. You have to bend them 90 degrees once the legs are through, but its easy to then have the front row of legs folded down shorting to the back row legs soldering points. They come with legs pre bent in a way you don't want, so takes some careful fiddling. I broke a few legs and ended up ordering more amp chips. Hope this helps someone

Sorry for bad picture, I had already put it back together and happened to have taken this one earlier

 

[beatnik]

Just in case anyone wonders across this and has the same issue as me (No blown fuse but power looping, LED swelling on and off and beeping sound).. I eventually got my broken one working again by replacing both amps (TDA7293) and this diode (30BQ100). I had a bunch of problems, most probably caused by myself, but eventually this is what worked out. Those amp chips are fiddly.. You have to bend them 90 degrees once the legs are through, but its easy to then have the front row of legs folded down shorting to the back row legs soldering points. They come with legs pre bent in a way you don't want, so takes some careful fiddling. I broke a few legs and ended up ordering more amp chips. Hope this helps someone

Sorry for bad picture, I had already put it back together and happened to have taken this one earlier

The amp chips come in two different mounting styles, the correct one is a drop in replacement.

In my case I also had to change the tda chips but there were power supply issues as well.

Unsure wether the failed amplifier caused the PSU to blow up or vice versa.

If I'm not mistaken Neumann has released an MK2 of this model. It would be interesting to see the difference.