Epson ink jet print head basics

Date Posted: 09/03/2004

Before deciding to replace a print head on an Epson inkjet printer, please read the following and make sure you've eliminated the easy answers!

This information assumes you're using Epson brand ink cartridges. If so, we've found that the heads seldom fail completely, beyond the point of being recoverable using Epson's cleaning fluids. Poor print quality is often the result of the head, capping assembly or pump tubing becoming clogged. Usually this occurs because the printer simply isn't used frequently enough or has sat idle too long. If ink remains stationary it tends to crust over anywhere air can get to it.

If you're not using Epson brand inks, whether it's just to save money---understandable, but based on our experience, bad for the printer---or because your application requires "special" ink such as dyes, sublimation inks, food coloring etc., you can almost count on the head(s), cap and pump clogging up. For many businesses using special inks, these parts become "consumable" items and somebody on the staff becomes a part time printer technician. We're here to help!

The following basic checks are executed at Compass Micro to determine what parts are required to fix a Stylus printer that will not print. (This is somewhat long winded but stick with it, you're bound to learn something.
You may save yourself the expense of an unnecessary print head!) Assuming, for the moment, the printer has a good supply of ink, the first step is to print a "nozzle check" pattern
to determine which nozzles are firing and which are not.

A nozzle check can be printed from the printer driver. After printing a nozzle check, run a cleaning cycle then print another nozzle check to see if any nozzles cleared. If nozzles are clearing a couple cleaning cycles may do the trick.

Don't overlook the easy answer! We see a couple printers a month that need nothing more than this. It's also worth mentioning that cleaning cycles will use up your ink in a hurry! Use some discretion here.

If you've cleared most of the clogged nozzles and are down to a just a few stubborn hold-outs, let the printer sit overnight. Gravity sometimes does wonderful things! Or, just start using the printer for draft work and you may find the last couple nozzles clear up with use. If your nozzle check print outs have gone from bad to worse, you may be running out of ink.

Make sure the ink cartridges still have ink.
It may sound silly, but many of the printers we see are out of ink! This may be true even though the ink status displayed on your computer's monitor indicates otherwise. The ink status shown on your computer is only a mathematical representation of numbers read via the signal cable from the printer's memory. Among a multitude of adjustment values, head voltage values and other code, the printer has ink "counters"---one for each color of ink your printer uses. These counters keep track of how many cleaning cycles you've run as well as the tiny volumes of each color used on each print job. In theory, a very accurate number that triggers a light or warning when you're running low on a particular ink. These counters, however, can be corrupted in a number of ways, depending on the model in question. This is one reason Epson tells you not to remove the ink cartridge unless you are installing a new cartridge---playing with them can cause the counter to reset incorrectly. If, for example, you take out a half empty cartridge and put it back in, the logical counter changes to "full" on some models and the status given on your computer follows suit.

Newer model Epson printers use "smart" cartridges. These have the ink counters built into the cartridge itself. The status displayed on your computer monitor is still taken from the printer's logic board but the ink cartridge is the source. This makes it impossible to accidentally reset the counters but the system can still be corrupted. The ink counters on the printer's logic board are updated every time the printer is turned off, but only if it is turned off using the printer's on/off switch. If you shut it off using a power strip, or any other external switch, the printer's normal power down process is bypassed and the logic counters are not properly updated. If the printer is shut off via an external switch all the time, the logic counters may never decrease.

Based on all of the above, it is our opinion that the best method for determining whether an ink cartridge is truly empty or not, is to compare its weight to that of a full ink cartridge. If it feels empty, start by replacing the ink. (Here, again, the logic can trip you up! On most models, the instructions for changing the ink cartridge assume that you have a red light or error condition indicating the printer is out of ink. If this isn't true---if there is no error condition---the button it tells you to push will probably run a cleaning cycle instead of triggering the head to move to the ink changing position. If you experience this catch 22, try holding down the paper feed button instead. On many models, this will cause the head to move over and allow you to change the ink.)
If the printer has ink but the nozzles will not clear by running cleaning cycles, we then clean up the capping assembly and look to see whether the pump is working properly.

Now we're getting into disassembly.