I’ve found these machines to be among the better color LaserJet printers made. When OEM cartridges are used, I rarely run into problems and these printers require very little maintenance, most of which a customer can handle on their own. I have a few of these machines in the field right now that have over 1,000,000 prints. I believe these machines are well worth keeping around, if possible.
In follow up to Monday’s post, here are a few more troubleshooting tips for the 4700 LaserJet and the 4730 MFP.
HP Color LaserJet 4700 Light Print CMY Color Planes
A recent service called involved a machine that was printing light in all the colors. When I printed a config page I noticed that all the colors seemed extremely light. The printer error report showed lots of CPR sensor errors and 54.XX halftone calibration errors.
The customer had replaced all the color cartridges (they were using OEM cartridges). Disabling the cartridge check in the diagnostics menu and swapping the cartridges, restoring the print quality settings, running a full calibration, and making sure its toner save was turned off did nothing to change the print quality. I took out the feed assembly under the cartridges and cleaned out the two color plane registration and density sensors. Once again, nothing changed on the print quality.
As a last resort I performed a NVRAM RESET to clear out the color calibration settings in the DC Controller. Once again, running the calibration after start up the machine printed light so I reset the NVRAM again then turned the machine off once the display read READY before it did a calibration. On start up I entered service mode and told it to skip the calibration. After I reset the NVRAM and skipped the calibration the machine printed fine.
The problem was gone for now but I knew the issue would come back once a calibration was run. I knew the information given to the DC controller from the sensors was wrong and that lead me to think either the transfer assembly or the calibration sensors had gone bad.
After further research I came across this service note from HP. The solution per this document is to replace the transfer belt. The customer happened to have a transfer belt on hand and once I installed the new transfer belt and let the machine calibrate the problem went away.
The reason you get ‘poor calibration’ errors when the transfer rollers in the transfer belt don’t engage is that the colors get a poor transfer to the belt leading to abnormal light color blocks as the sensors try to calibrate. Below is a link to new transfer belt if needed.
Q7504A Image Transfer Belt/kit for Color Laser CP4005, 4700 and MFP 4730
Tray 4 Feed Issues on the Color LaserJet 4700 Printer
I wouldn’t expect to see this issue on a lot of machines but I ran into it recently. I have a customer who has a fully loaded 4700 printer with the 3rd and 4th feed tray. My customer was complaining that the machine was having issues feeding out of tray 4.
At first, I thought it was just a simple case of installing some new feed rollers but after installing new feed rollers in tray 4 I was still having feed issues. Upon servicing the machine I noticed that when feeding from tray 4 the paper was jamming in the transport area from tray 4 and 3. Through further diagnostics it became clear that the transport roller on the top of the tray 4 and 3 feed assembly were shot. In order to fix this issue the whole optional feed tray has to be replaced.
Remember, I did say this probably won’t be a common problem because, the fact is, this particular machine now has over a million prints on it and obviously most of those have come from tray 3 and 4.
Q7499A 500-Sheet Paper Input Tray/Feeder Assembly for Color LaserJet CP4005 & 4700
Gray Background on Labels and on Color Machines
Gray background on labels has always been an issue on laser printers. Often I go into a customer’s office to work on their printers and get questions about their labels having a gray background. Of course, they’re not happy that they have to throw half a sheet of labels away because they look so bad. What I always find is that customers are using a full sheet of 30 to 50 labels and printing off one label at a time then feeding it back through the next time they need one. While this practice is not recommended by HP and other manufactures I can understand why customers do this. However, that’s what creates this problem.
Little do people realize that often times when you print a sheet of paper, especially with third party toner cartridges, there is a little background toner dropped across the whole page. When the paper is fed through once it’s next to impossible to see the background. But feed it through 20 to 30 times and it becomes a lot easier to see, especially on labels. Usually after about 5 to 10 times it becomes obvious you have a “dirty” background. The best thing I can say to reduce this problem is to only use OEM toner cartridges and make sure that whenever a transfer roller is replaced in a PM kit that it is replaced with an OEM transfer roller.
I’ve also seen this problem on a few color machines I’ve worked on lately with just plain white paper. Once again, the problem seems more pronounced with third party cartridges. The problem that I’ve had recently with machines like the HP Color LaserJet 4700 is that if you do a half test and stop it half way through the fuser, it looks good on the side not fused but once it gets fused it looks really bad. Upon further investigation I noticed that there was a background issue on the paper that wasn’t apparent at first glance but once it hit the fusing unit it really emphasized the problem. The customer was using reconditioned cartridges so I went through and changed out the cartridges one at a time and sure enough after each replacement the image appeared better. I will note that in most cases when I’ve seen this issue the cartridge or cartridges have been on the verge of being empty.
Kevin Gumpp is a certified printer technician and freelance writer for Market Point. If you have a question regarding this topic or have any other printer repair related questions or topics for which you would like more information, please send an email to firstname.lastname@example.org.