Part replacement is a valid procedure but a "costly" one if one blindly go about it. What I am suggesting is understand how overload is triggered. As far as I know from the manual block diagram overload is from the preamp up to the tube driver V1. I have traced overload from J44 to J23 and it's accompaning schematic and it leads to the logic, slewrate sensor, input divider and input fet Q121.
You have to know the function of Q121 as per the manual. It is a "gate" for 5200A if used. It controls the input with it's associated circuits ( temperature compensation & gate drive ). you have to think like CSI the crime drama how it all started.
Forensic thinking? Ask yourself how would overload be triggered. Is it normal component failure or user induced by pluging 5200A and feeding 5205A an improper signal or voltage or stand alone usage.
PS the triggering ogfhigh votltage K1 relay can come from initial internal tests during turn on. Read minor and major fault and it's solutions.
EDIT: Also check for cracked solder joints with such old equipment as you go about inspecting any particular
circuit you think is suspicious. Actually it should be part of the initial visual inspection procedure. The fault may just be a simple circuit wiring break.