HP 6978 not printing black ink. Colors are printing but absolutely no black ink. I've tried all the fixes suggested by HP support, including, but not limited to, multiple (12X) printhead cleaning and still no printing black ink. I have tried copying also and it still does not print black ink. This is the second HP 6978 printer I've had with the exact issue. I tossed the first printer and replaced with another only to end up the the exact issue after 18 months.