AB SLC-150 CPU fault

Hi, New guy here.

We have older Allen Bradley SLC 150s in our six Automated mini-load supply units. One unit tripped a CPU fault, and will not reset. We have tried known good units from supply and from other mini-loads. PLC does the exact same thing and then is fine when reinstalled in the other machine. All 115AC and 24VDC power inputs and sensor input/output values are correct. Double checked all wiring and encoders. Tried swapping out the Eprom, no dice. We hooked up the pocket programmer to try to clear and put it back in PC run, but the programmer will not communicate, Error 10. Has anyone ever seen a situation like this? I'm thinking it must have a hard short somewhere, but we've disconnected everything on the input side.

Thanks in advance....

Have you tried removing all inputs and seeing if it would reset?

Normally the fault would not be because of an I/O I would think a value in the CPU, program error or loss of program.... BUT maybe the encoder input

When you changed the CPU did you try the other one in the other machine?

Have you tried to bench test the faulted PLC? By that I mean just connect the power only from an isolated power supply to the plc and the programmer to see if there is something on the machine causing the problem. Also, I'm guessing that you tested the programmer on a known good PLC to verify that it can communicate.