I'm usually pretty handy but I gave up trying to fix this problem. However, I loved the cartridge cart on the 7510 (so easy to remove and clean) so I looked for other HP printers that used the same cartridges. Walmart had a sale on refurbished HP 5520. They were practically giving it away for around $50. Heck, the new cartridges alone were worth 20 to $25. I bought refillable cartridges and it has been running beautifully for the past 6 months.