HP 761 DesignJet Maintenance Cartridge. OEM:CH649A. You rely on your Designjet T7100 for productive, high quality print output when creating large format documents. Keep it operating at peak performance by installing this HP 761 Maintenance Cartridge, an essential piece of kit for trouble-free, smooth operation when you need it most. Slotting into the right side of your printer, this cartridge assists in cleaning the printheads to prevent clogging and blockages from ruining your prints. It also helps seal the printheads when not in use to prevent them drying out. Make sure you replace the maintenance cartridge as soon as possible when alerted - leaving a used cartridge in the machine can result in serious damage.