SLC power supply trouble

Hi, I have a system that consists of the following
1746-p1
slc 5/04
Slot 1 1746-ni4
Slot 2 1746-ib8
slot 3 n/u
Slot 4 n/u
Slot 5 1746-ob8
slot 6 1746-ob16
I found the plc to be dead on arrival check voltage to power supply 220v jumper set correctly. Replaced fuse but blows again 3amp fast acting. Decided to pull the power supply and test on bench again replace fuse this time fuse would not trip but the power supply would not power up. Replaced the power supply with a spare 1746-p2 powered up the unit, plc leds lit up for about 2 seconds and went dark. Fuse on the power supply did not trip however it does power up when bench tested. This system has been in operation for a 6 years no problems. Anyone ever experience something like this. My thoughts are that there is something going on with the analog module but not sure where to test next. All the dip switches are set to 4-20 ma and all channels are used. I will be testing analog field devices next. Any help greatly appreciated.

You can ty removing the cards one by one until the problem goes away. I would suspect the backplane is bad in this case, try putting a different backplane on the power supply.

It has been my experience that the power supply is the most likely component to fail in an SLC system. That said, power supply voltage being pulled down usually points to a damaged I/O module or chassis. Rather than removing modules one by one, I usually just remove all of the modules and then replace them one by one in such a situation. Remember this also -- when you find the culprit, don't assume that it is the only one. Test all of the modules.

Thanks for your help this turned out to be the chassis. What was surprising to me that it took out two power supply's.