How to replace 6400 fuse

No unsoldering is necessary. Remove the top cover with a T9 Torx bit. On the 6400, remove the two coax cables (very gently pull straight up) and make note of where they go back (LPF X2, RXA X7). Gently unplug the ribbon cable (PA X4). Remove the four phillips-head screws from the filter board. Remove the four phillips-head screws from the SO-239 antenna connectors. Gently ease the board back and out. The rivets holding the coax connectors can hang slightly on the mounting studs, so a little wiggling may be necessary.

Now the fuse is in plain view and can be replaced, if needed.

Put the filter board back in (making sure that all cables are accessible) and put all the screws back in only finger tight. Then tighten the SO-239 screws first so that there is no stress on the board. Finally, tighten the screws holding the board down followed by plugging in the ribbon cable and two coax cables.

I don't have an ATU or a 6600, so there may be more connections and another board to deal with, but I would think the process is generally the same.

I didn't need to change my fuse but did this exercise to understand what I need to do in the field should anything bad happen requiring a fuse replacement. My truck and camper both use this same fuse size, and I have plenty of 30 A replacements on hand, therefore I will never need to replace it...