Printer won't print using black

Question

My printer won't print black. The black ink tank is held in a seperate removable printhead (a BC-30e). The red/mag/cyan have a printhead (a BC-31e) of their own that they occupy together. I have purchased a new black printhead and put that it and put in the new ink tank, but still it won't print black. All the tabs are removed...I've had the printer for a few years now...so I know I put everything in correctly.Do you have any ideas? Could some of the electronics have gone? Or maybe something needs a clean - but what? Would appreciate any ideas you can offer. Thanks.