L6598D SMPS For B&W Sub

[hazmoment]

So I'm attempting a repair on a B&W Sub.
I found the issue to be the SMPS is not generating the DC Rail the amplifier board requires. On closer inspection I found the switching Fets had shorted. So I replaced these along with the L6598D IC just in case.
Short now gone, but still no DC Rail. I connected my scope probes up to High and Low Side switching pins of the L6598D but no switching going on. Just some noise.
I replaced the IC again to eliminate the possibility of it being damaged/ faulty and Its still not switching.
Pin 12 Vs - is 15v dc or so which seems standard. But dont know how to further check this circuit. had there got to be an enable signal present before the IC will start switchinf. If so, where would this likely be coming from?

I happened to also find a 2.2R 5W ceramic resistor had open circuited. This is in a strange location in the circuit to me and I dont understand the purpose- It is inline with the AC Live conductor before the Full Bridge Rectifier and a SPST relay is in parallel with it.  So when the relay is energised the 2.2 ohm resistor is shorted out. And when open the AC current goes through the resistor. This has been replaced too, but hasnt helped with the issue. Hope someone can shed some light on this!

[Swake]

That 5W resistor and relay combo is likely an inrush current limiter. It keeps the resistor in the line for a second or so to avoid blowing fuses in the house when the big transformers/coils/caps take a charge at startup.

Magic crystal balls are becoming scares these days. Without more info on the exact device or schematic we can't help much.

Check for the datasheet of the L6598D, it might help out.