It’s fairly simple in design (see diagram at the end of this post). A motor turns some gears that in turn rotate the shaft the rollers are attached to. In theory the design’s use of force makes the media in the tray inconsequential. No matter what media is being used, from tissue paper to card stock labels, the Autocompensator will deliver it to the imaging part of the printer one page at a time. Also, in theory, the Autocompensator cannot fail. In theory.
From the Lexmark Optra S to the Lexmark T630s the Autocompensator had a spring operated clutch on the roller shaft that only allowed the shaft to turn in one direction. That made it real easy to troubleshoot. The spring clutch, gears, motor, etc. rarely fail. However, the rollers get slick and then can’t move the media from the tray to imaging. Thus, you’d get a paper jam error but no jammed paper could be found. Simple fix: replace the rollers and all is well with the world.
One common problem to avoid is installing the rollers on the wrong side. They’re directional. Look at the sides of the rollers to observe the direction of the arrows. Always make sure they are pointing toward the front of the printer.
The worst thing to happen with the integrated Autocompensator is the post on the Right Side Frame Assembly breaking off. That’s where the Bias Spring for the Bell Crank Assembly attaches to the frame. If this plastic post breaks, the Autocompensator will fall to the bottom of the tray and not lift when the tray is pulled out. When that happens you’ve got 2 options – if you’ve got a T630 model:
1) Replace the printer, which is not really a cost effective option and hard to sell your customer;
If you own or are repairing a T640 or later you have two options as well:
1) Replace the printer. No joke. The frame assembly has no part number and no support from any supplier I know of, including Lexmark. Also, the Right Side Frame Assemblies are not swappable. There are enough changes to the T640 that the older assemblies won’t work. Two screws are completely different and the top left, as you’re looking at it, is rounded in the T630 and flattened in the T640. It would make enough of a difference that the front cover wouldn’t close right.
2) Try this procedure: Cut, sand or grind the post as smooth as possible. Drill a 1/8th inch (3.2mm) hole where the post used to be. Use a self-tapping screw at least ½ inch (12.7mm) long. I suggest you drill all the way through the frame. You’ll have enough in the frame to hold the screw and enough out to hook the Bias Spring on. Watch for splintering and cracking at the hole’s location. If that occurs refer to option 1.
With the T640 series came the bearing clutch shaft. And it continues with the T650s. The little housing that the bearings operate in is pressed together (and not very well). It can open just enough for one or more of the bearings to fall out and render the clutch inoperable. It will periodically and momentarily stop turning and not feed the media. Once again, you’ll get a paper jam error with no paper to be found. Troubleshooting that problem is fairly simple; just turn the roller shaft quickly — like it should operate — and you’ll find that it binds and sticks every once in awhile. That’s when the error occurs.
The easiest fix I’ve found for this is replacing the bearing clutch shaft with the old spring clutch shaft. Which, by the way, can’t be ordered from any vendor I know of. It has to come from a machine that you can cannibalize. We usually have a couple of these in the attic. They are almost a necessity if you’re going to work on Lexmark printers. To remove the shaft take the rollers off, hold the gear housing and gently but firmly push the shaft to the right. It’ll eventually pop out. It takes two hands and some patience but it’ll happen, trust me. Then take the spring clutch shaft and push it into the hole in the gear housing from right to left. It’ll pop right in and work like a champ for a very long time.
If by some happenstance the little hooked piece of plastic that holds the rollers on the shaft breaks, you can temporarily fix that with a cotton swab. I carry them for cleaning tight areas so there’s a supply either in my kit or my car. Break off the cotton end and stuff it, stick end first, into the hole created by the missing latch on the end of the shaft. It forces what’s left of the latch out enough to keep the roller in place until you can get another shaft.
A good improvement to the Autocompensator came with the T650s. The roller. It’s got horizontal, rounded ridges instead of microscopic teeth to grip the media. It’s been my experience that these types of rollers last literally years. They require cleaning every now and again, but rarely need replacement. A good design improvement. And although they look like they might not fit earlier models, they do, and they work beautifully. So the best combination I’ve been able to put together is the spring clutch shaft with the ridged rollers.
Happy customers, happy service guy.
Brian Ude is a certified printer technician with years of experience. Brian serves Western Office (www.western-office.com) in Billings, Montana. If you have a question for Brian regarding this topic or have any other printer repair related questions or topics you would like more information on, please post a comment on this blog or send an email to firstname.lastname@example.org.