My controller S4C+, Manipulator IRB 140, System 6811-2.25
Where is problem?
I changed ;
DSQC 500 (Main Computer)
DSQC 501 (Backplane Unit, in PC),
DSQC 504 (Base Connector Unit),
DSQC 509 (Panel Board)
DSQC 506 Main Supply,
Harddisk,
Pc Power Supply,
Teachpendent,
remove connection of floppy disk,
change manipulator but error not solved. Please help ! 
You have checked/verified voltage levels on the main board?
What I notice is the BaseWare 4.0 rev125 (6811-2.25). Anytime I've used software over rev92, it's always had the DSQC540 processor. Not sure if it matters.
The 3.3V & 12V supplies are from the Computer Power Supply and stay in the Computer Unit, they should not be effected by anything connected to it. Your list shows you already changed it.
I would concentrate on the connections and boards in the Computer Unit. Measure the voltages at connector X1 going to the backplane. If any voltages are low, try removing the Axis CPU and the I/O CPU to see if one of them is loading down the supplied voltage.
I've had (2) DSQC532 I/O CPU go bad in the same week this summer but 200 miles apart. They both loaded down the IDE bus.
Good Luck!!
Thank you for your interest. The fault was from the DSQC500 card. I tried 2 DSQC500 cards. I changed the bios battery on both cards. The fault has been solved. 
