modern switching power supply faults

I have two Dell switchers out of P4 based 1U servers. The first one has a failure in the startup circuit... pressing the power button will lead to a flash of the power light... and that's it. The second one failed spectacularly.... There is a wire wound power resistor (5W15RJ) near the AC input... it cooked... and I do mean cooked. It came out in pieces (with almost no effort), melted the nearby capacitor and a nearby relay. It also did a pretty good job of puckering/burning the PCB (but not bad enough it could not be used). I suspected maybe shorted primary full wave rectifier... but I used the DVM on diode test and got what I'd expect. Oddly, despite there being a fuse on the primary side... it's still good... it wasn't taken out. That resistor got hot hot hot. Could that resistor have failed on it's own ? I suspect something further down the circuit must have a problem. I'd be happy if I could make one power supply out of the two. These are not simple supplies however. While much of the switching transistors, regulators, bridge rectifiers, capacitors and the usual fair in a switcher are pretty readily identified, there is a 6" x 1" "brain" board (I'll call it that as it has adjustment pots, the ps fan circuit, quite a # of surface mount components on both side of it, and it interfaces with the main PCB with 34 connections. These are Dell W5916 supplies. Unsure who really makes these for Dell, only other marking is Model: HP-U280EF3. Both these supplies had been cycled 4 times on/off the mains due to a power failure (power fail, generator cycled on, power restored, generator cycled off, repeat process one more time) within a few minutes of each other. The first one was dead immediately after this (the one that has a problem in the start circuit (or a monitor/etc is shutting it down when it detects a problem during turn on). The second one failed almost two weeks after. I know this isn't particularly classic... but I know that there are those out there much wiser than me in switchmode power supplies. So lets pretend it is 2014 that way the supplies will be 10 years old :-).... -- Curt