After four new black toner cartridges, my printer is still saying to replace the black toner.  I am using a Dell cartridge since I thought maybe the generic ones were to blame but no different.  It's driving me crazy.  I've taken the cartridges out, shook them, tried to clean out the excess toner laying in the printer, etc.  What's left?  I really need to get this fixed as soon as possible.  Is there a repair person or place to take it to or does it go into the dumpster??  Thanks!