Printer and Photocopier Troubleshooting and Repair Collection : Diagnosing 'blank copy' problems        
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Diagnosing 'blank copy' problems

"I have just cleaned a Sharp SF 755 which was quite dirty but now will not copy at all! No error codes paper hot on exit, all seems well but the paper is blank."

(From: Bruce L. Miles (henry31@prodigy.net).)

Two things to try:

  1. Peek inside and see if you can detect a latent image on the drum. If an image of your test document exists on the drum, then the main corona unit is working at least.

  2. Perform a 'Skyshot Test'. Leave the cover off the glass and take a picture of, well, the sky. It is a good idea to cover the leading edge (left side) of the copy glass with a piece of paper so that the fuser doesn't try so hard to jam on a solid sheet of heavily tonered (blackened) paper.

If the skyshot print comes out white (it should be entirely black since the amount of light hitting the drum compared to reflection from actual copy is nil), and you DID have a latent image on the drum, the prime suspect would be the transfer corona - it is not receiving the high negative voltage needed to pull the positively charged toner off the drum and onto the paper. The culprit could be the corona wire being broken, the corona assembly not making a good connection into its high voltage socket, or even some weirdness going on with the high voltage power supply - i.e., supplying proper voltage to the main corona, but nothing to the transfer corona.