Step One
It wasn't either of the fuses, neither the plug nor the PSU.
Next, to find a soldering iron and reattach the fuse to the PSU. I've performed this operation before, even though, in truth, I wish I hadn't had to (it's a long story).
Following this, to check the power wiring, which isn't as nicely organised as it once was. But having detached the fuse, and having, at present, no soldering iron with which to reattach it, I can't check the power wiring for functionality at this point. Khan, etc.
Following this, something on the motherboard having broken is a serious and worrying possibility, not one I want to have to consider. But I'd already poked at the wiring while the PSU was still in the machine, so I know that it's unlikely to be that. And with the machine not turning on at all, I'm not getting any information at all for diagnosis. This is less than helpful.
Next, to find a soldering iron and reattach the fuse to the PSU. I've performed this operation before, even though, in truth, I wish I hadn't had to (it's a long story).
Following this, to check the power wiring, which isn't as nicely organised as it once was. But having detached the fuse, and having, at present, no soldering iron with which to reattach it, I can't check the power wiring for functionality at this point. Khan, etc.
Following this, something on the motherboard having broken is a serious and worrying possibility, not one I want to have to consider. But I'd already poked at the wiring while the PSU was still in the machine, so I know that it's unlikely to be that. And with the machine not turning on at all, I'm not getting any information at all for diagnosis. This is less than helpful.