Does using non-HP cartridges void my warranty?
No, the use of a non-HP cartridge or a refilled cartridge does not affect either the warranty to the customer or any HP support contract with the customer. However, if printer failure or damage is attributable to the use of a non-HP or refilled cartridge or an expired ink cartridge, HP will charge its standard time and materials charges to service the printer. (Page 3)
From the official HP Officejet Pro 7720 Wide Format All-in-One Printer manual, page 3
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