Behringer PMP6000

[daveball]

The Output stage is oscillating on this mixer even when the mixer section is disconnected.Has any one had this problem

[mozwell]

power amp is class D, so try using a dummy load & check the output voltage across the dummy load.
All the switching from the output mosfets should be filtered by L1, C19, L2, C14, C15, C131, R8, R12, if you have no dummy load, you may just be seeing the power amp switching getting onto the speaker terminal, we need the dummy load (or speaker) as part of the filter circuit.

Here is the sch, for reference, the power amps are on the first page