HP M4345 Multi-Function Printer, Printing Blank Pages!

Contributed By Jonathon Barwon

We have a huge contract with a UN Organization to maintain and service about 91 printers, copiers, scanners.

During our last maintenance visit we routinely serviced a HP M4345 MFP and carried out a regular test print. The user signed off on our maintenance log and all was well.

About a week later we got an email from the client that the printer was printing blank pages and they started blaming us for this problem. They said that they had tried to replace the toner to no avail. I was dispatched by my Head of Operations to go and check out what may be the issue.

On arrival my first observation was that the client was using fake toners. I straight away condemned the toner and told the client that if we get a genuine toner from our stock the problem would be resolved. The client accepted and we sent for a Genuine HP toner.

To my utter shock and embarrassment, on insertion of the Genuine HP toner the machine rejected it and we got a message on the printer: “ Remove Orange tab”, this was already removed before the toner was inserted into the printer, and all of us were surprised and confused on what may be the problem. The client mocked me and said that your toner too is fake and that the printer was not able to recognize it!!!

We brought the printer to our lab and got down to diagnosing the problem.

We had some spare parts available and swapped the main PSU (Power Supply Unit), the High Voltage PSU, the scanner board, the DC controller and the formatter. We also swapped the transfer roller. 

All these ideas did not help at all.

On a thorough examination, my Head of Operations noticed that there is a spring on the left side of the printer that should make contact with the toner sensors. He suspected that this may be malfunctioning. He called up HP tech support in the USA and they advised that the problem may be due to a broken laser shutter flag.

I decided to go back to the client to inspect another similar printer to see if there is indeed any laser shutter flag in a working printer, and to also check the spring. And lo and behold, I noticed that the spring in the working printer was placed quite differently than the spring in our faulty printer. I quickly rushed back excitedly and placed the spring back correctly and carried out a test print.

Guess what? The printer is now working perfectly well. Imagine what one tiny spring can do? This spring was apparently dislodged when a user jammed in a toner cartridge. When dislodged it was right down below the white piece of plastic, whereas the actual position should be above the white plastic.

See picture below.