MW12CX Output blown

[Calder]

I have a Yamaha MW12CX mixer that has been great for 10 years. Recently, on the monitors output, one side of the stereo output has become crackly, distorted and nasty. I also noticed some crosstalk on the headphone output the other week. When I noticed the crosstalk, I started plugging my headphones into the monitors (they have an output for headphones). So I’m aware that the issues with the monitor output could be that I overloaded it with my 80ohm headphones!

I’ve ordered two replacement op-amps – one for the monitor output and one for the headphone output. The signal going to Stereo Out and Record Out is as clean as a whistle so I am assuming my problems must be related to these op-amps or possibly the caps around them. Does this sound about right? Is it more likely to be the opamps or the caps?

I have a thermal cam on the way and the components will likely take a few weeks so I have not yet opened up the mixer as it’s still in use for voiceover work.

On order so far I have: 4560R BA4560RF-E2 for the monitor output and NJM4556AL for the headphone output.

Circuit diagram attached.

Any help / ideas would be very welcome! I can’t afford to buy a new one so fixing this is my only option.

Attachments:

1. 

   MW12-Monitor-HP-output.pdf
   

[abrsvcs]

Defective OPamp ICs are the most common cause of distortion like this. Replacing the ICs would be the first thing I would do in this case. If you have a scope, you should see a good signal going into the IC and distortion going out. While unlikely, the coupling caps may also be bad. Check those as well.

Dan

[Calder]

Thank you 🙂 I did buy a DCO Shell a while back. Ill probe those inputs when I open up the case – thanks so much for your help.

Calder

[Author]

Posts