January 2003 Featured Technical Article

Drum Reset Problems on the HP LaserJet 8500 & 4500 Series

Imagine you’re faced with the following situation: A customer calls telling you their HP Color LaserJet 8500 is displaying a “Drum Life Low” message. You suggest they should use the drum until it is fully expired—unless they are having print problems. The customer tells you it is printing fine, but the configuration menu indicates the drum life is nearly exhausted, to which you tell them you are on your way! You arrive at the customer’s site just as the image drum is running its final print and displaying "Drum Life Out,” at which time it stops printing.

To begin, you remove the old image drum and install the new one, making sure not to turn off the power, because you know there are jobs in the printer memory which would be lost if you did. After installing the image drum and closing all the doors, the 8500 begins to print again, but the “Drum Life Out” message continues to be displayed. The customer now asks you why the message is still present, to which you are not sure how to answer. Though you have installed the image drum kit on an 8500 before in situations just like this, the message has always cleared. Is it a bad drum? Is there a reset for some versions that you aren’t aware of? Should you send the drum back?

These are pretty common questions, and realistic to ask yourself when you come across this problem. As it turns out, there is a collection of HP LaserJet 8500 and 4500 printers that do continue to display “Drum Life Out” even after the drum has been replaced. I’m sure many of you reading this are thinking, “They should have powered down the printer before installing the drum unit,” but according to the instructions, this is not necessary. You should be able to install the new image drum and the message should disappear. The image drum count is kept via a smart chip in the image drum cartridge. This means the image drum can be pulled out of one machine and placed into another, and the correct count will be kept with it. For the other kits—transfer and fuser kits—the counts are kept in the printer’s non-volatile memory. If someone moves those kit components from one printer to another, the counts are not kept with the units and the kits will either run a longer or shorter life depending upon the counts in the machine they were put into. This can cause obvious problems, such as parts running longer than their rated life, causing an emergency call when they fail, or replacement before their full life has been used up.

For the end user who wants to run the HP LaserJet 8500/8550 transfer or fuser kit past the end of their life, they can set the “Toner Low” option in the printer menu to “Continue.” The service message will continue to appear but the kit will run beyond its life.

Some end users who grow tired of the service message will reset the maintenance count in the resets menu, starting the counter over again. This is typically followed by a phone call by the customer stating that the print has deteriorated, and questions as to why they did not get a service message when the printer needed the replacement kit. The HP LaserJet 8500/8550 image drum becomes the exception to this “continuation” past the kit life. With the counter in the drum cartridge—and no reset for it in the menus—when the drum runs out, the end user must replace it to continue printing.

So why are some printers displaying the message even after the image drum in replaced and others are not? This is likely a programming error in the firmware, which could be in either the formatter ROM firmware or DC controller firmware. Regardless, the simple remedy to the annoying message is cycling the power once the printer memory is free of print jobs. For all the machines we’ve encountered with this problem, cycling the power has reset the drum kit maintenance message once the new drum is installed.

Do note, as mentioned earlier, some HP LaserJet 4500 printers have had this same problem, but setting the “Toner Low” option in the menu of the 4500 or 4550 to “Continue” does not allow the fuser kit or the transfer kit to run past their life. HP also built some protection into the ROM firmware that stops a technician from rolling back the maintenance count in service mode once the service message appears. Basically, you must reset the message or live with it until the kit components are replaced.

Another aspect of the image drums of the HP Color LaserJet 8500 & 4500 series printers deals with some complaints customers have had about the life of the drum kits. Some customers believe they are not getting the full life out of the image drum before the “Drum Life Low” or “Drum Life Out” message appears. The 8500/8550 drum kit is rated for 50,000 pages for black and white (B&W), 12,500 pages for color; the 4500 drum kit is rated 25,000 pages for B&W and 6,250 pages for color. Notice the four to one ratio between B&W and color. Since both the 8500 and 4500 series of printers use four color process, it takes four “life” rotations of the image drum when printing in color. B&W would only take one “life” rotation, thus when printing in color, the drums have a shorter life. Customers who tend to complain about the short life are often customers who are printing color in duplex mode. If you think about it, a duplex page is one sheet of paper with color prints on two sides—thus eight “life” rotations are used up on one sheet. Most customers will look at the short stack of paper and wonder why the drum life is not meeting expectations, but not comprehending the cost savings in using a duplex unit.

The drum message problem is a bit of a headache-who wants to tell a customer they need to cycle the power on a machine at the end of the day? Considering the impressive color capabilities of these printers, I think we can live with a few quirks—as long as we know how to deal with them.

—Steve Geishirt

Mr. Geishirt, as Director of Training for Parts Now! has provided laser printer and technical training for over ten years.