Why is the black not printing in a HP 309A printer?

I have cleaned the HP309A printer's printhead (CN642A) per HP instructions, aligned the printer and inserted new HP564 cartrindges. The cartridge alignment failed. The 3 color cartridges are printing and I was able to use the blue cartridge to print a spreadsheet. What other corrective actions are possible? Is it worth purchasing a refurbished printhead (CN642A) and what is the probability that the printhead is the cause of the problem?