I get this question frequently from owners of Lexmark T series printers. (T620, T630, T640 and T650 series – all types.) The most common problem with a leaking cartridge is the waste bin of the  cartridge has become full and will begin to dribble out onto the paper and all over the inside of the printer.

Let’s take a quick look at the printing process.  Here is a simple explanation on laser printing.  Open up your printer and pull out the toner cartridge and look in the top for the charge roller and the bottom for the transfer roller.  Basically the toner is moved from the “hopper” to the drum and then to the paper.

We can break the printing process down into 4 steps: Charge, exposure, transfer & cleaning.
First there is the charge. In this step the drum is electrostatically ‘erased’

Charge roller is visible when the toner cartridge is removed and drops down from above the cartridge.

by the charge roller while it rides right on the drum.  Once it’s fully erased it can be exposed.

The drum is exposed by the laser beam drawing an image on the drum.
Quite simply, wherever the laser hits the drum, toner is attracted to that spot. The drum continues to revolve as it’s passed close to the paper.

The transfer roller sits below the toner cartridge

Once near the paper, the third step occurs: transfer. Toner is transferred from the drum to the paper. The transfer roller sits under the paper with a strong opposing electrical charge and pulls the toner from the drum and onto the paper. The drum continues its revolution and is cleaned internally by a wiper and any excess toner is wiped off and deposited into the waste bin.

Now, here is where the problem occurs. When the transfer roller gets worn out, less toner makes its way on to the paper and toner left on the drum is cleaned off. The result is that more toner is going into the waste bin during the cleaning wipe.

Diagram of Lexmark T series cartridge parts

Why does the waste bin become full?  Well, there is a limited amount of space in the waste bin and once this bin is full, it has no other place to go and begins to dribble out.  When a transfer roller is new your prints will be very dark, crisp and will transfer nearly 100% of the toner from the drum to the paper. Over time the roller will wear out and less toner will get transferred to the paper and will be wiped off the drum with each revolution and end up in the waste bin.  One solution is to keep your transfer roller fresh. If you see lighter copies, change the transfer roller right away. Try switching from the extra high yield cartridge to a lower yield cartridge.  Here is an example: If you are using a 32,000 page extra high yield cartridge the waste bin on this cartridge is exactly the same as one found on a 21,000 page cartridge. More prints means more waste so you may be more likely to fill the waste bin inside a 32K if your transfer roller is only transferring 70%-80% than with a 21K.

You can order roller kits for your Lexmark T series printers here
Maintenance kits contain the transfer roller and can be ordered here

by:  Thomas Braeger