I have an older HP LaserJet4+ in our shop. It has a JetDirect J2550 installed. Other than that it is configured as factory stock. This printer has a total page count of approx 119490. It prints a 1/16" thick horizontal line on the print, including test pages. The printer has NO pattern to this issue. This pattern will reappear randomly at the following spacing 1.5", 3", 4.5". I have looked in the service manual and do not seem to find an possible cause for this problem. Any educated suggestions?
Thank You,
Wallace Gustafson