That makes me an old Fossil
the S3 system was launched while I worked for ABB, in fact when I started it was ASEA Robotics and I learnt programming on the S1 system!.
Haha cool, you are one of the old guys in the game. it was back in the Esab/Asea days, i love the old s2/3 they are so easy to fix when they break down because you can measure everything on them.
I did not knew of that SAABoholic, so thanks
I never use this method, just know its possible. normally i use pc interface.
You can't connect a pc to an s3, the code so old you can't even open it on a pc.
The error you get is a com. problem between the Main computer and robot computer, how many electrical cabinets do you have? only one or 2?
I would check the connections on the back of the boards, turn of the power, pull them out and give them some contact cleaner.
totally of topic, you say your a student, why are you working on a robot from the 80's?? that thing should be in a museum
EDIT:
DO NOT disconnect the maincomputer or the battery, then you have to reboot the system 
What exact year/model is it?
On the old 6400 its in 99% the cable chain in the socket of the robot, take of one of the covers and look inside, if there are pieces of cable insulation there, its a new cable harness.
If you suspect the drive unit, just shut down the controller and switch them (6400 uses the same driveunits in all 3 places) Driveunit A2 is for axis 4/2, so switch nr2 drive from the right with number 1 or 3, A0 is the DC-link and not a drive unit. then you can see if the error has moved with the driveunit or is still on axis 4.
It's true what SAABoholic writes, but you can acces the controller on your factory network via the serviceport as long as you only got 1 controller on the network because you can't chance the IP settings for the service port, otherwise you can get a converter you plug directly on the serviceport and to an outgoing internet connection, i use that a lot of places where i need to go online on robots without PC interface.
The correct way is however:
Get the option PC interface
Reboot the system with the new key.
X-Start the system (hit ABB/Restart/Advanced/X-Start) select fixed IP and enter IP, Subnet, gateway.
Put the cable from your factory network in LAN on the main computer (not the serviceport)
This i for RobotWare 5, on 5.6 and 6 you got multiply Lan on the new main computer (DSQC1000) so there you need to set the right one up.
officially It's not possible to use other flash cards then ABB's, unofficially is another story, but its not easy.
Its the same with the workobjects (unless its a mowing wobj) go to program data, wobjdata, create af new, press define.
You need some kind of pointer on the robot tool, jog to points X1, X2, and Y1 and modpos them.
I have attached the user manual, look under 6. Programming and testing, and 6.4/6.5 (tool/wobj)
What du you mean by calibration, the only thing you calibrate on an ABB are the motors, like if you replace one.
Do you mean defining the tool and workobjects? (so the robot knows the tool center point)
Works with older versions to, i run 5.14, 5.15, 5.61, and 6.3. Even robinstall for S4C+ works on win 10.
You need 3 connections, the Serial cable from the axis computer needs to go from there to the SC and from the SC to the robot SMB plug on the cabinet, a Ethernet cable from the main computer to the SC and then to the Axis computer. And a 24Vdc molex plug on the top of the sc controller.
You also need supply on the green pheonix connecter on the SC (pin 1 and 2) if you dont you will get the "SC1 supply failure" everytime you restart the controller. if you dont need it, just reboot the controller with a new system and remove the X in safety controller, take out the controller like roulv says, its behind the axis computer.
Then you dont have to think about soft/hardware sync.
If you dont need EPS/Safemove, remove it!
I/o plus dont work on 3.0, on 3.1 only for one waggo unit. it is not really supportet before 3.2, and you can't upgrade to 3.1-2 from 3.0 without new main- and robot computer.
Are you talking about a mec.unit (like a multi axis positioner), or a robot, if a robot what model? you can't count on the calibration. you need to tjek the difference from absolute zero on the old mec unit and the new. the calibration is rarely the same as it was from the factory, if you replace a motor you recalibrate it, if it is mounted on af track you recalibrate axis 1. even if the calibrations is correct on the new, who says it is on the old.
Best Regards
Emil
ABB Robot Technician.
