Laser printers provide excellent print output on paper in both black and white and full color. Laser printers use a fairly complicated printing process that techs should understand. This video details the processes and components for techs to maintain and service all sorts of laser printers.
in old tech are terms like paperless office. I remember, I'm serious, kids, in the mid-1980s where people were talking about how paper is going away, and it's just a matter of time. Well, ha! I can't tell you how much money I've made fixing printers in those 30-some-odd years. So, in this episode, I want to talk about probably This is what we call a photosensitive drum, and this is the cornerstone of all laser printers. You see, the idea behind laser printing is that you can use a laser to hit that little photosensitive drum. Now, that photosensitive drum can hold an electrical charge, a static charge, but the more light it sees, the less of a charge at that particular spot it can hold. Using that technology, we can do some amazing stuff. So, let's talk about the laser imaging process. So, this is my photosensitive drum, that green thing you just saw. Well, virtually everything that has to do with laser printing happens on this drum. So, what we start off with is what we call processing. So, print jobs come in from different computers and they're stored in memory on the laser printer. For the most part, with laser printers, the entire job comes into the printer and then it's actually printed. So, the printing process begins, first of all, by charging one spot on this guy with a primary corona. The primary corona puts a uniform negative charge on this. Now, keep in mind, there's different parts doing different things as we go. So, right here, here's the primary corona, and he puts, it depends on the brand, but anywhere from a negative 400-volt to a negative 600-volt charge. So, before we go any further, let me put out a quick warning here. Sticking your hand into an operating laser printer is a really bad idea. We're talking about extremely high voltages, or extremely low negative voltages, same thing as far as being electrocuted comes. We also have to deal with extremely high heat and rollers and things that are pinchy and painful, so before we even say anything else, never stick your hand into a functioning laser printer. Okay, let's get back to the process. So, now that we've got this negative, say, I'm going to for this example say negative 400-volt charge, as it rotates, the first thing that's going to happen is we're going to have a laser begin to write whatever the image is onto the photosensitive drum. You can't see it. It's just a difference in charge. So, wherever it's hitting it with the little tiny bits of laser light, it's going to go from, say, negative 400 to about a negative 150-volt charge. Again, if you could see electricity, you could actually see the letters being written at that point. So, now, the next thing we're going to do is go into developing. At this point, what's happening is your toner is sitting at around a negative 300-volt charge. Now, I want you to think about this for a minute. If this is negative 300 volts and the unexposed part is negative 400 volts, that would be very negative, and negatives avoid other negatives. It would be repulsed from the area that wasn't exposed. Where it is exposed, it's a negative 150 volts. So, even though the toner is negative 300, at negative 150, that's a positive, it's less charge, so the toner's going to be yanked out of the toner pile and it will stick wherever we had the exposed image. So, now we literally have loose toner sitting on the photosensitive drum, and at this point, if you could get your eyeballs in there, you could actually see your words. So, now as it continues to turn, the first thing we're going to have is our paper coming in. Now, as the paper comes in, first of all, we're going to have pick-up rollers and then we're going to have separation pads, or separate pads. Basically, the pick-up roller grabs the paper and the separate pads pushes on it so that only one piece of paper is grabbed at a time. but they add a little bit more, simply because, instead of just having black toner in them, they have CMYK. So, cyan, magenta, yellow, and K is for black. So, these different colors of toner, we have four toner cartridges in there, well, they need a little extra help to get all the different colors onto one piece of paper. Let me show you how that works. So, the only big difference with a color laser printer is we've got these four different hoppers of colored toner. So, what takes place is that we don't just have a transfer roller, but we usually have a transfer belt. So, what takes place is each one of these passes close to the transfer belt, putting their particular color onto the belt. Now the belt has all four colors, and then we go through the transfer process to go ahead and put it on the paper. Because of the built-on nature of laser printers, they're probably one of the easiest in terms of maintenance. However, I should also add that laser printers, especially big office laser printers, are expensive and deserve a little bit of good treatment. So, a couple of things we need to think about. Now, everybody talks about the toner cartridge, but if you think about the toner cartridge, pretty much all the work is done inside this toner cartridge. It's got the photosensitive drum, it's got the toner in it, and this is where all the work takes place. And that's a nice part because, as this photosensitive drum begins to wear out, we just replace it with a new toner cartridge. So, you're not just getting new toner, folks, you're getting the new photosensitive drum. You're also probably getting some pick-up rollers, a few other things like that that are all in one very convenient little piece like this. But that's not the only thing you need to deal with. The other thing that laser printers are going to need is ongoing maintenance. Now, ongoing maintenance, number one, is going to be cleaning. Read the documentation for your particular laser printer, and they all have some fairly specific cleaning processes. Now, I know in other episodes I say never use a vacuum cleaner, this is the one place where I will make an exception. A lot of times, in order to get into specific spots on a laser printer, you must have an anti-static vacuum. Again, go ahead and read your documentation and see what you need for your particular system. The other thing that comes into play with laser printers is the concept of maintenance kits. All laser printers have maintenance kits. These maintenance kits are almost always going to consist of, for example, a bunch of new pick-up rollers. Pick-up rollers are notorious for catching paper dander, and over time, they just stop picking up. You get a maintenance kit on there, and all of a sudden, you replace those guys and you replace some separate pads, and next thing you know, all of a sudden it's working great, picking up paper perfectly. Also, you might see another maintenance kit that might have a transfer roller or something like that in it. Everybody's different. When you apply them is different, how often you do them is different, but every single laser printer out there, especially the more expensive office brands, have very specific maintenance kits that are usually applied after a certain number of prints. Now, you can go into any laser printer you want and go into a maintenance mode where you can actually tell the laser printer to print out all its vital statistics. How many printing jobs has it done? How old is the actual printer itself? Lots of information like this, and it actually will help you. And some printers will even post up a screen that says, please apply maintenance kit 1493 or something like that. These maintenance kits are easily available. You can pick them up from the manufacturers, although personally I like eBay, they tend to be a bit cheaper, and it will do miracles for you. I have an original Hewlett-Packard LaserJet 3. LaserJet 3, from the mid-1990s. The thing is a tank, and the reason it runs so well is because I've given it good maintenance over the years and the thing still does a great job even today, and Hewlett-Packard still sells maintenance kits for them. The last thing you need to consider, and that is pretty much unique to color laser printers, is the concept of calibration. Over time, you can have issues, primarily with your transfer roller, that it will have issues that the different colors of toner are not hitting perfectly. They all have a built-in calibration feature. You run the calibration, you run a few pieces of paper through it, and it fixes itself. These few basic rules, if you remember how to do this and you, too, will have really old printers that work so fabulously well, you'll just keep them forever. (upbeat music)
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