If the PSU model is psu3300-03 then I think it should be compatible.
About your logs ECHU and ECMM is pointing to your control board or connection problem that is why you get -273.
If you have extra control board try to switch it or try to reflash your unit because bootby shows abnormal value.
thank you. I only have 1 a1246 I do have the correct spare psu.
I will try that.
edit:
I found Avalon buddy it reads psu is failed.
I will drive to the mine over the week and replace it.