I am evaluating a design for a 24 VDC output, universal input power supply using the PFS708 eval board RDR-248 supplying 380 VDC to a LCS702 eval board RDR-239.  I am powering the set-up through a LISN and monitoring the conducted emissions with a spectrum analyzer.  I am also using a small magnetic field EMC probe hooked to an oscilloscope to look at localized time-domain currents on the PCS PCB.  I see peaks related to harmonics of the 256 KHz switching frequency of the LCS supply, the PFS on its own driving a resistive load is very clean.  I see ringing at 35 MHz at both the input and output of the transformer T1 at twice the operating frequency of the LCS; the 24 VDC output appears clean.  I have tried various snubbers and ferrite beads at both the rectifier diode D2 and the primary side of the transformer T1.  So far, nothing has improved the ringing or the LISN conducted emission harmonic emissions.

Any ideas?

Thanks.