Behringer Pmx660m Power Amp Help

[Gabriel Diorio]

Hi everybody! Please i need help of yours. I´ll appreciate you colaboration. Sory my english is nt good. I´ve a PMX660M powered mixer, the power supply and power amp has failed, i suuspect of a mains fail (in the power supply, caps and transistors are blown, in the power amp, one of two channel blown the MOSFET and resistances). Has been repaired and operational, but:

When load is connected, the FBQ leds blinking without control, and the power amp is shutdown before to reach the maxium level output. While happen this, just before shutdown, the audio is distorted, generating audible "peaks" in the speakers. In the oscilloscope, i see the peak, the signal raises instantly to +V. Below of this peaks, the audio is perfecly clear and no distortion.

Two things: 1) when the mixer section is powered by another external power supply, the FBQ led are steady ok or working well.
2) i´ve tested with main and monitor output to load other amp and work ok without problems. For this i´m discarted the mixer section for this problem.

I have, tanks to this wonderful forum, the complete schematics of the circuits (SPS400 power supply and DPA300 power amp) , but i need help, i´m checking the components and all are ok. Only the main IC on the power amp (HCA4001) is not tested yet, but, all voltages in this are nominal.

What can be this problem? SOmebody has experienced with this modules?

I´m very appreciate you help!

Regards for everyone from Argentina!


Gabriel.