When the fuse blows, that means there is one or multiple shortcuts down the line. This can be on the main board, in the flat cables or in the head. You should never expect to fix it by only changing the fuse, you might just make things worse.
If the fuse blows without prior human intervention that usually means the shortcut is inside a head and that head has to be identified and replaced. Sometimes the fuse will blow a bit too late, meaning that the big transistors on the main board are damaged, causing another shortcut.
If the fuse blows following an intervention (usually head or dampers replacement), that means the shortcut is due to the flat cables being damaged or improperly seated into the heads, or some ink has been spilled on the heads. Again the transistors on the main board may be damaged (that applies each time a fuse is blown).
When changing a fuse on the main board you should always check those big transistors with a multimeter if you know how to do it. Alternatively you can replace the fuse and unplug the heads corresponding to the failing group by completely removing the flat cables. Then you turn on the printer, print a nozzle check and turn it off again to check the fuse. If the fuse is blown then the main board is damaged. Otherwise the shortcut is further down the line meaning that if the flat cables look good, one of the heads is damaged.
You can then plug one of the heads and try the nozzle check again. If the head fires, then the unplugged head has to be replaced. If it doesn't fire, then the fuse and the plugged head have to be replaced and the main board should be checked again.
