Coombs' test involves taking a blood sample which is checked for the presence of antibodies which may destroy red blood cells.
You can use the HP Print and Scan Doctor to test the status of the printer spooler, print queue, device manager, and device conflicts. 1  On the desktop, double-click the HP Print and Scan Doctor icon to open the tool. 2  Click Start on the Welcome screen. 3  Select your printer, and then click Next.  Click Fix Printing.
Being an HP user you might have heard of HP Print Diagnostic Utility. However, this is not available for older products and for Mac users. Download the tool if you have a Windows-based PC and run it to fix various print errors instantly.