Lines on Print with HP M551

[user544]

Hello,

As an update, in the hopes that this might lead to some more troubleshooting ideas.  Back on Monday of this week the printer hadn't been used for a couple days.  First print of the day was an invoice.  The printout contained two vertical lines and each line contained short color segments.  I'm attaching a photo.  Note that I had to redact portions due to the document being an invoice, but you can see that the lines get darker towards the bottom of the page.

The next print didn't have any lines.  This is consistent with the behavior.  A larger print job yesterday, duplex, first two pages had black lines on each side but by the third page there was no evidence of an issue.

Is there some mechanism by which this printer is depositing toner when idle or during calibration, etc?  Other ideas?

Steve

[PSSG]

The printer is not depositing toner when it is idle.  The laser scanners charge the toner cartridge drums.  The toner cartridge drums apply toner to the charged drum areas.  The transfer rollers inside the belt press down causing the image on the toner drums to transfer to the transfer belt.  When the paper passes through the transfer belt and secondary transfer roller, the image is transferred to the paper.  The fuser melts the toner into the paper.  At the conclusion of this process, the toner cartridge and transfer belt cleaning blades remove toner from the drums and belt.  The majority of lines, like your printer's lines, are caused by either a toner, belt, or fuser.  Your printer's defect is interesting.  During transfer belt calibration, a color pattern is placed on the belt to allow the printer to calibrate the color printing process.  The color marks in your paper's lines look like the calibration pattern.  I do not have a theory on how this is happening.  A defective power supply or laser scanner may produce a solid black line.  I do not remember ever replacing these parts on this model.  First, upgrade the firmware:

https://support.hp.com/us-en/drivers/selfservice/hp-laserjet-enterprise-500-color-printer-m551-serie....  Then perform three consecutive full calibrations.  Print a test page.  If print defect continues to occur on the first two pages, print a test page and stop the paper when the leading edge of the paper is at the secondary transfer roller.  Just open the right side door.  Then, inspect the toner cartridges and the belt.  This half test used with the disable cartridge test should be sufficient enough to identify cause of line.  Good luck. 

[user544]

Thank you for this detailed explanation.  I updated the firmware and ran the three calibrations.  Ran Print Quality troubleshooting pages and the printer is doing its normal lines on the first few but then nothing on subsequent pages.  We let it 'cool down' for a few hours and then did the stop test but the line didn't show up on the top half of the first page.  I'm going to let it sit overnight and run the stop test immediately again first thing tomorrow or Monday to determine if there are any unfused toner lines.

Based on the result of this initial test, I ordered a fuser kit direct from HP just now.  It's odd to me that the fuser would play a role but it's trivial to swap it out.

Steve

Steve