HP C7180 All-in-one Printing Problem

My HP C7180 All-in-one will no longer print black. Colors work fine.
I have done all the usual things, including a hard reset on the panel,
updating the driver, using a new reservoir, cleaning the print head
multiple times (via the menu). The contacts are clean, the reservoir
is full. I suspect that the print head may need a manual cleaning.
Can anyone tell me how to do this? Replacement print heads cost more
than the machine is worth. HP email techs have been no help so far.

Thanks.

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