SC540 Head not firing, advise Please

I just posted about a headsoak, but have a more severe problem. One of my heads is not firing at all, no ink at all, and another is only firing on half. Ive changed caps, cleaned, and changed ink dampers. Pulled ink through lines to dampers ok. no ink on print head electronics, reset cables, to no avail. any ideas or any other troubleshooting ideas? Ive changed heads before, ebay ones and those are still working fine. Using third party inks and havnt really had any problems with them and have used them for a while. Anyway to trouble shoot heads?
Thanks

 

Also, I saw in another post to check fuses. I dont see any fuses on the mainboard. Im not sure if this is the old board, permanent fuses, or newer board, replaceable fuses. Does anyone know where these fuses are.