Most laser printers on the market today use a computer chip to tell the printer/computer when it's empty. The chip does not have any kind of physical sensor to tell whether the toner is actually low or not, instead it keeps track of how many pages were printed using the toner cartridge. (there is a separate chip on each cartridge, so in a color printer there are 4 chips one of each color and one on the black)
The chips tell your printer/computer that they are low or empty long before the toner is actually low or empty. If you replace them when the computer tells you to you are throwing away a lot of good toner.
To make things worse, the printers will not print at all (color or b/w) once it believes that one of the cartridges is empty.
There are 2 ways to 'trick' your printer into not believing that a cartridge is empty.(Solution 1)
The chips that are on the cartridges can be swapped out with new ones. There are several vendors that sell aftermarket chips for your 2550 toner cartridges. Do a general search for 2550 reset chip and you will find vendors that sell reset chips. You can also find them on eBay for around $20-$25 a set.
The chips themselves are very simple to replace. Use a small screwdriver and pry off the old chip. They are just held in place with a strong piece of double sided tape. If the old tape is still there and good, you can just put the new chip in it's place, otherwise stick the new one on with some double sided tape.
This trick can also be used to extend the life of your printer drum, as you can buy reset chips for it as well.(Solution 2) A bit clunky, but this one is free
You can literally trick your printer into not reading the info from the chip and thus not stopping you from printing. This solution is not as nice and clean as the first one, but it does work and it's free. You will have to repeat this solution from time to time if the printer stops working.
- Step 1: Power off your HP2550 printer.
- Step 2: While the printer is off, press and hold the big green button on the printer.
- Step 3: While still pressing the green button, power the printer back on using the power button (lower back corner on the left side of the printer).
- Step 4: Continue to hold the green button while the printer initializes. During this time all of the front lights will turn on one at a time and then all but the first green light (the ready light) will turn off one at a time - this step can take several minutes to be patient and keep holding the green button.
- Step 5: When all the lights have turned off except the front green light, release the big green button. The front lights with flash a few time, while they are flashing, press and release the red circle button 1 time.
- Step 6: You may have to reload the printer driver at this point. If your computer has detected new hardware then go ahead and reinstall the driver.
- Some of the back cartridge lights (the back 4) may stay on or flash, this is OK.
- The front green 'Ready' light will no longer be on, again this is OK.
- If at any time your printer stops printing all together, then go through these steps again. I have had to redo this about 10 times over the past 2 1/2 years. It is a nuisance, but it saves a great deal of money.
- If this does not work the first time then try it again. Each step must be done in order and correctly otherwise it does not work.
I have had my printer for almost 3 years now. The original cartridges that came with my printer stopped working because they told the printer they were empty about 2 1/2 years ago. I started doing this at that time and all 4 of mine (I have a 2550 color printer) are all still working and have not started to fade, so there was a lot of toner left when my printer said it was empty.