Digital BW, The Print

I have a 2200 that I use for BO printing with MIS eboni ink.  I
recently switched out all the color carts with blanks filled with MIS
cleaning solution.  The nozzle check right before this showed some
clogging on the black cart only, and after the switch the clogging got
worse and worse until no black came out at all.

Since that time, I've tried a bunch of cleaning steps culminating with
a careful and complete disassembly of the printer and thorough
cleaning of the print head.  I have pumped cleaning solution through
the print head and can verify that none of the jets are clogged.

The printer is now in pristine condition and hums along flawlessly. 
However, not a drop of ink makes it to the page when print.  When I
print a black purge image, nozzle check, etc., all I get is a blank
sheet of paper.  I've tried this with the MIS mk cart as well as new
genuine epson mk and pk carts (there goes another $20).

Is there something else that can go wrong with print heads/printers
that I don't know about?  I really don't want to spend the $189 to
repair it.