Going to cost you

Our printer went in for repair and the "Printhead Assembly" returned to us as we booked the unit in. Few days later we received the quote that the "Printhead assembly " needs to be replaced. As we needed the printer for tender purposes we gave the go-ahead for the repair. NOW how did they find that the Printehead assembly is faulty ? They returned the printer with a new printhead assembly + an old faulty assembly ( probably another customers faulty unit ) The printer worked for less than a week and the exact same fault code appeared again. Sent it back under warrantee but now suddenly its another component thats faulty - ADF Scanner assembly . AND WE NEED TO PAY AGAIN !!!!! PLEASE TELL US HOW YOU FOUND THAT THE PRINTER ASSEMBLY WAS FAULTY IN THE FIRST PLACE IF YOU NEVER HAD THE ASSEMBLY IN YOUR POSSESSION !!!!!! MAKES YOU THINK DOESN'T IT