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Optra S & T Image Defects

18 Mar, 2001 By: Steve Geishirt imageSource

Optra S & T Image Defects

This winter has been a cold one, which is not news to most of you reading this article. The cold is often associated with dry air, particularly inside as we continue to heat our buildings and dry them out even more. This dry air in winter, and dry air in the summer for other parts of the country, are well known for creating print image defects. One in particular we have seen and heard much about is on the Optra S & T printers. The problems that customers have been having are on the order of light repetitive images of the previous rotation of the image drum, what we call “ghosting.” Another symptom includes dirty background on the page, as if a light dusting of toner is left all over the paper. In this article I’d like to explore what is going on here and the solutions to it, including parts replacement procedures.

The Basics Of Optra S & Optra T

If you’re not real familiar with the Optra S & Optra T printers, you’ll find there is something unique about them when it comes to the toner cartridge. All other single cartridge type printers contain the toner, electrostatic image drum, charge roller and waste toner hopper unit all in one. You may be surprised to find the Optra S & T toner cartridges do not contain the charge roller. Normally, when I tell people that, they wonder how the charge is applied to the image drum. There is also a charge roller; it’s just not a part of the toner cartridge. The charge roller is broken out independently and sits above the toner cartridge. You may not have noticed it before because as you open the top front door to remove the toner cartridge, there is a lever mechanism that lifts the charge roller up so it doesn’t get damaged. If you remove the toner cartridge and slowly close the top front door you will notice it dropping down into place to make contact with the missing image drum.

The Job Of The Charge Roller

This roller is still considered a supply item and will wear out over time. In its normal wear and tear process, the most common symptom is dirty background print (note one of the symptoms listed above). So what does the dryness in the winter have to do with these print problems? Well, this goes back to how the image is formed in the first place. If you remember your basic laser theory, the written image on the image drum is an electrostatic image. The job of the charge roller is to apply an even charge field of static electricity across the surface of the drum. The laser is then used to discharge areas of this static charge field so toner can be attracted to it in the developing process. This discharging occurs when the image drum surface reacts to the laser light and becomes semi-conductive, that is specifically where the light hits the drum. This change in the drum surface allows a path for some of the static charge to discharge through and travel to the core of the drum, which is connected to ground.

Charge Variance

Many of you who have been working on HP and Canon printers for years are knowledgeable of this basic laser theory, but what many don’t know is that Lexmark uses a different range of charges in creating these images. The Canon engines have traditionally been placed at 600 volts negative static charge on the image drum, depending on the printer. Lexmark applies a charge closer to negative 1000 volts evenly across the image drum. Of course these charges only apply to printers that use charge roller technology and not corona wires. This –1000V charge also changes all the other charges in Lexmark’s laser theory, such as in the writing stage where the interaction of the laser beam and drum reduce the static charge to about –400V and the Canon engine to about –100V. In the developing stage where toner is attracted to the discharged areas of the drum, the Lexmark version has toner charged to about –700V, as opposed 300V for the Canon engine. Lexmark may have figured these charges would make a better combination to create prints. With the exception of this situation and other normal toner cartridge related problems, the prints coming from the Lexmark printers are pretty sharp and clean.

Moisture In The Air

So, how does the presence, or lack of presence of moisture in the air affect the image? While I was hoping to give you a more atomic description of how this happens, it is probably best to put in the following manner:

The static charges sitting on the drum are basically charged air particles. The added moisture in the air helps it to be more conducive to accepting and holding the static charge. Thus, lack of moisture means the air is less conducive to accepting and holding the static charge on the surface of the drum. The result is a lesser charge on the surface of the drum. As the static charge drops closer to the -700V range, toner alos becomes attracted to it and the background of the image becomes dusted with toner. This dusting effect is not uncommon in the development process, but when it becomes thick enough on the drum, the dusting will transfer to the paper and be noticeable. This is when your customer has problems.

Ghostly Images

This lesser charge on the drum surface due to the lack of humidity in the air also results in poorer cleaning of the previous image. This poorer cleaning can create ghost like images of the previous rotation of the image drum. Part of cleaning the image off the toner cartridge drum is done by the erase lamps located just before the transfer roller. This exposure of light discharges much of the rest of background, and helps in the separation process at the transfer roller. The second part of cleaning the old image off the drum (for what was not erased) is recharging the toner cartridge drum at the charge roller. If the charge roller is not properly charging the drum due to dryness and general wear and tear, it may not fully cover over the old static image on the drum allowing it to reprint in this ghost like manner.

In severe situations, installation of a humidifier to add moisture to the room can make a great difference. I have spoken with technicians who tell of trying to convince customers to add a humidifier to a room to improve the print images; customers can’t seem to fathom this. A service tech informed me of one customer that went ahead and bought a humidifier and installed it right under the table that the printer was on, just to prove to the technician it wouldn’t fix the image problem, but it did.

One of the more common fixes for these symptoms has been replacement of the charge roller in the Optra S & T series printers. You may ask, “Why not just add a humidifier to the room like the example above?” The problem appears to be a combination of wear and tear on the charge rollers in conjunction with the drier environment. In other words, just adding moisture to the air will not necessarily fix this situation.

Interchangeable Rollers

The big question we have been hearing out on the street is, “Will the Optra S charge roller work in an Optra T printer, and vice versa?” Both charge rollers have different part numbers from Lexmark, so they must be different right? We find these two rollers are interchangeable not only by physical dimensions but also by their performance. This big question is due to the large demand for these rollers and in some cases, lack of supply of one or another nation wide. The part number of the Optra S charge roller kit is 99A1033 and the Optra T charge roller kit part number is 99A1017. Again, both of these rollers and kits (as that is how they come), are interchangeable. In fact, the 99A1017 kit that we opened for picture taking contained both the Optra S and Optra T door tools along with instructions for both printers.

The rest of this article will go step by step how to change the charge roller in an Optra S or T printer, and how to use the included tool.

1. Remove the toner cartridge from the printer

2. Use the included tool to partially prop open the top front door as seen. This allows easy and steady access to the charge roller.

3. Reach into the printer and remove the old charge roller by gently pushing the right arm that is holding the transfer roller away from the end of the. This will allow one end to drop down, and the other end to easily slide out of the other arm.

4. Take the new charge roller and DO NOT remove the paper that is wrapped around it.

5. The paper keeps the roller clean as you install it into the printer. Install the roller by inserting the left end into the arm and the gently bending the right arm to attach the other side. Once installed, you can now remove the paper.

Note: If you touch the roller with your bare hands, the oil and dirt from your hands can cause print defects. These defects may not show up in simple text prints but are much more noticeable when printing graphics. Some people have cleaned this roller with isopropyl alcohol and have had some success when in a bind; however, this is typically not a long-term solution. Be careful what you use to clean this roller because any residue you leave behind will also make contact with the toner cartridge drum. If that chemical reacts with the drum you can ruin the toner cartridge. Chemicals such as ammonia products, often contained in window cleaners, can destroy the toner cartridge image drum.

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