behringer UB2442fx Pro mixer - clicking / popping noises on outputs

[jnsomerville]

Thanks, I am relatively familiar with SMPS. I note however that 12V on this mixer seems to go to main board as well, obviously i'm seeing it on this supply as it is devoid of a voltage regualtion circuit, whereas i'm not seeing the variations on the stabilised supplies, which you'd expect. Thats not to say that there isn't noise, just not obvious.

I have been trying to source the filter caps but finding them is proving difficult, I've tried a number of component retailers, Farnell ? grandata etc, but no luck yet.

Youve been really helpful thank you.

[jnsomerville]

well, I have changed all of the caps including the mains filter ones, all of the IC / transistors, all that is left now are the chokes, the transformer, R1 10ohm resistor, bridge rectifier RS205, VT1 and diodes and I still have the clicks and popping / hissing and crackling noises but thay all appear to test ok dry, I can't see why any of these components could be causing the noises .... i'm scratching my head once more!

[jnsomerville]

Well everything other than transformer and chokes now replaced on the hot side, but still pop in and cracking.... I'm bemused really

[Jazz P Bass]

Maybe the problem is Not on the hot side.
Just a thought.

[diydidi]

Are you able to run the power supply outside of the mixer, and add load resistors ~56ohms or so to the ±12Vrails?
You can then scope to see if its the power supply or not.
Also you van power the mixer from an external ±12V bench supply if you have one.