FORCE YOUR DESIGNJET PRINTER TO ACCEPT INK CARTRIDGES, even if it thinks they are empty, or if it's rejecting 3rd-party cartridges. 

All you have to do is pull the right end cover off. No soldering required, no permanent modification to the printer required.  Guaranteed for life.  

-FREE FIRST-CLASS SHIPPING INSIDE THE UNITED STATES

Is your printer telling you "ink cartridge empty," showing an "X" on a cartridge, or otherwise not accepting ink cartridges? This is the solution. Sometimes the printer will get picky about what cartridges it accepts, and sometimes aftermarket cartridges just aren't built right, so the printer rejects them.

The mod chip does not do anything to the ink cartridges themselves. Rather, this mod chip allows you to use ANY cartridge by tricking the printer's logic into thinking there is a FULL set of HP OEM cartridges installed at all times (even if you remove the cartridges from the printer altogether). For this reason, DO NOT START PRINTING WITH THE CARTRIDGES OUT OF THE MACHINE, as this will starve the printheads of ink. When the mod chip is installed, the printer can't tell if ink cartridges are present or not. It will simply perpetually believe there are full cartridges present. The ink supply station, however WILL continue to pressurize the ink cartridges as usual, allowing for safe, continuous use of the printer. 

C4844A Modification Chip for HP Designjet 500, 510, 800.