Charging System Life Extension

                            By Raymond Cote

Is it possible to get a million impressions from your photoreceptor (1R88) belt?   The answer is yes and no. And that depends on how you set the charging system up. Let’s take a moment to explore what we are thinking about. Usually the life expectancy on a photoreceptor belt (1R88) in your Xerox 5090 family of copiers is between 400,000 to 600,000 impressions.  And in your Docutech, and 4135 printer you can approach one million impressions before replacing the photoreceptor belt.  I have had numerous independent technicians tell me that their 5090 (family) photoreceptor belts have been reaching one million impressions and the Docutech, 4135 (family) have been approaching two million impressions before the photoreceptors were replaced.  Impossible you say? Yep, I agree with you on this one.  Let’s read on!

When I started to investigate the longevity of photoreceptor belts the independents were a multitude of information and they had their own secret recipe for extending the service life of the photoreceptor belts.  I would like to pass this information along to the field in an effort to reduce photoreceptor usage and improve copy quality.

If you do your cost accounting, and keep accurate records on what you spend in repairs you will note that the Charging system will usually account for (about) 9 to 10 percent of the total expenses for service parts on the 5090 family of copiers. When we take the charging system into consideration we will be including the following components: HVAC Power Supply, all the dicorotrons, The HVAC and HVDC PWB’s, The Ozak system, the MIN ADA PWB’s, DIO PWB, and the DC spider Connection.  These parts must work together to provide the proper current (and voltages) to the photoreceptor belt, and to transfer toner to the paper, and to provide the proper currents to the preclean dicorotrons.

Keep in mind, the harder the charging system has to work to do its job, the sooner the charge components will fail.  When we look at the charging system, working harder will usually mean generating higher voltages and currents. If, for example, we could get the charging system to operate at lower voltages and currents the components and sub components will last longer. Seems simple doesn’t it?

One of the ways we could extend the life of the components is by raising charge efficiency, and reducing (to a great extent) contamination. The changes included the following components: TAG 199, Charge (Chopped) Dicorotrons (125K1450), and TAG 222 Air Dam with a (chopped) Dicorotrons.

Chopped Dicorotrons have a yellow body to distinguish them from the regular white dicorotrons.  The difference is the yellow dicorotrons are 1.55 mm shorter than the white ones. They actually sit (about) .55 mm closer to the photoreceptor belt, and the Coro node wire is about 2.00mm closer to the belt. Conversely the Preclean dicorotrons is 4.0 mm closer to the belt as well.

When we lower the dicorotrons height (from the photoreceptor), the dicorotrons becomes more efficient. It can do the same work consuming less voltage. This efficient operation will increase the life expectancy of all the components and sub components in the charging system.  The HSFI interval for the chopped dicorotrons is much higher. Charge 1 dicorotrons HSFI goes to two million copies, and charge 2 HSFI will increase to three million copies.  When the Dicorotrons have to be replaced just order the Coro node wire part number 48K56790 and replace the wire.

A lower charge voltage will mean less charge is on the photoreceptor belt. And while operating at lower voltages it will extend life expectancy of the photoreceptor belt by minimizing 09-203 and 09-204 Xerographic system faults until much later in the service live of the photoreceptor belt.  By moving the Coronado wire closer to the photoreceptor belt means there will be a greater charge efficiency, and longer service life of the belt.

Height Adjustment:

For the tech that has the adjustment section in the service manual, it is recommended that you follow the adjustment procedure.  If the adjustment is not done properly, charging will not be efficient and parts will fail much sooner, and your service costs will go up. There are just two adjustments for the dicorotron height: the inboard adjustment and the outboard adjustment. The inboard adjustment is usually much more difficult to do because you are on your hands and knees with your arms extended all the way inside the cavity. With your flash light in your mouth and both hands trying to reach the nuts on the other side of the machine you look like something praying to the Xerographic god.

Keep in mind that when you move one adjustment the other end will move as well. It is almost like a child’s see saw device you see in the local park. I will usually do the outboard adjustment first because the inboard height can be set once.  To set the outboard height with the 10mm nut - This nut moves a slide block to set the height. Turning the 10 mm nut clockwise will raise the outboard end of the rail. Conversely turning it counterclockwise will lower the outboard end of the rail.

Next step: Adjust the inboard height next. This is not going to be easy, but there are two screws on the Dicorotron mounting bracket that are used to adjust the inboard height. One is an 8 mm screw/nut, and a 5.5 mm stop screw. To lower the inboard rail height, turn the 8 mm screw nut counterclockwise. This will loosen the screw/nut and allow the rail to be lowered. To actually lower the rail, turn the stop screw clockwise to the required height.

After setting the inboard height, double check the outboard adjustment again, since setting the inboard height may cause it to change. To make the final adjustment use the Xerographic test pattern to balance the charge uniformity.

If you follow this sequence- outboard (closest to you), inboard (rear of the machine), and outboard (again) will sort of guarantee that the dicorotrons will be set at the correct height on both ends.

Stray Light Strategy

With the Dicorotron height set properly the next thing we might want to look at is reducing stray light. It will be interesting to note that clean optics is quite critical to good image quality. It’s often times, when we are having copy quality problems, that we start thinking about dirty optics. The nagging question that comes to mind is how does dirty optics contribute to component failure?  And what about the service life of the Photoreceptor belt?

It’s interesting to note here that when the optics are dirty the charge and exposure will be too high, and in turn will cause premature parts failure in the charging system. We should examine how this happens and how the components are affected.

When the optics cavity is flashing away, light is traveling in all directions bouncing off everything in its path. It’s almost like a thousand ping pong balls in a laundry dryer bouncing all over the drum. Light reflected off the original document passes through the lens and onto the photoreceptor belt as a latent image due to the charge on the belt from the charge dicorotrons.  If the lens or document glass is dirty, dusty, or contaminated in some way and if the walls of the optic cavity are dirty this will have an effect on reflected light. This light (referred to as non-image light) sprays on the photoreceptor belt causing stray light.  The stray light that reaches the belt reduces the charge on the photoreceptor and washes out the latent image.

Reduction of stray light

Eliminating stray light is critical to extending the life of components in the charging system and the photoreceptor belt.  First we will look at the platen glass. Make sure it is clean on both sides and it is free of any abrasions from the document handler belts. Remove the glass and hold it up to the florescent lamps and examine it closely. While out of the copier, clean the lens (both sides) and make sure the seal on the lower tub is intact and not missing. The seal will help to prevent stray light from entering the belt cavity area. Use lens and mirror cleaner 43P8. Do not use Windex or any other type of commercial window cleaner. If you feel compelled to use a cleaner mix one tea spoon full of vinegar to one quart of water. Use a soft clean cloth and a few drops of the cleaner on the lens and platen glass.  Do not use Xerox Cleaner Formula “A”, or anything that contains ammonia or any chemical that you would not drink. The lens and the platen glass both have a special coating that will be destroyed with any harsh chemicals.

By reducing stray light you will help keep charge and exposure operating at its most efficient level.  The procedure will extend the service life of the charging system components and reduce your operating budget considerably.  The new optics cleaning HSFI procedure should be done at 6 million copies interval. NOTE: The stray light procedure should be performed on a routine basis and this is especially true in a dusty environments.

Docutech and 4135 family

On the Docutech and 4135 family of printers we do not have the optic cavity to be concerned with. But the adjustments are all valid to extending the life of all charge components.  On the bright side, when you are adjusting the Charge height in a Docutech it’s a piece of cake. Remove the top cover and the ROS assembly and you can work on the Charge rail assembly like a human being.  Always check the housing assemblies before you replace the Dicorotron wire. After removing the Dicorotron wire inspect the black coating inside the housing. Do not use water as it will wash off the coating and will destroy the housing.

There have been a few techs that have asked questions concerning flash lamp assemblies and how to extend them for maximum service life. Next month we will explore a flash lamp life extension strategy procedure.  Keep the comments and concerns coming.  It is always good to know that this column is helping out someone in the field.  I can be contacted at: VillageCopierNY@AOL.COM.

Raymond Cote can be contacted at Village Copier Service, 718-931-2830 • e-mail: VillageCopierNY@AOL.COM.