NR111D Step Down DC-DC: Output Won't Rise Above 6V, IC Fails With Higher FB Resistors

I am trying to step down 24VDC to 14.7VDC using Switching Regulator NR111D (8pin DIP)

I followed Typical Application Circuit Shown in spec sheet, and built it on a solderless bread board.  It works as expected and Vo=5VDC.

I then change the resistors in the FB pin voltage divider to change the Vo to Vo=14.7VDC.

The Spec sheet formula whould have me change R4+R5=20.7K Ohm to R4+R5=69.5K Ohm

I can't seem to get the Vo to rise much above 6VDC and as I increase the resistance of R4+R5, the IC blows (makes a pop sound and stops working).

R6 is unchanged from 3.9K Ohm

The rest of the circuit is as drawn up in the spec sheet.

D1 was un detailed so I am using P6KE550CA (I had some left over from another circuit, very similar).

 

What in the world am I missing? Why doesn't this work the way I am expecting?

nr111d_ds_en

The P6KE550CA is a transient supressor, are you sure that is what you are using. You MUST use a Schottky diode, rated for the currents and voltages around the circuit, nothing else will do. Additionally, the inductor characteristics are very important, you must use a part rated for the frequency, peak switching currents, and resistance to get the best performance from the switcher.
One more comment, solderless breadboard is also no good, you have to do a PCB, using the layout as suggested in the applications information, switcher layout is critical, and very dependant on reducing strays, particularly in the high current loops, I imagine that a scope will show some atrocious behaviour around the circuit,
cheers,
Richard