By far the most troublesome part of these HP machines is the fuser and swing plate assembly. Due to the increased print speed of these models and the heavy usage the printers handle, the fuser and surrounding gears tend to receive a lot of the abuse and wear. Noise is the main issue. If you work on these machines expect to receive a lot of calls related to noise and jam issues in the rear of the machine. Mainly in this article I will focus on noise issues but I’ll also take a look at other problems related to the fuser.
For noise issues on the HP Laser Jet 4200 and 4300 printer series remove the fuser and check the blue clip on the side that has the gears.
When these machines were first made, the clip was made only out of plastic. Due to the high print speed, pressure applied and the heat generated when the printer is running, the clip will dry and crack causing the fuser to not fully seat inside the machine.
After removing the fuser and checking the clip, drop down the back door and feed the paper out the back. When the back door is down it applies pressure to the back of the fuser causing it to work again with the gears inside the machine.
The clip has been updated with a metal piece inside the middle.
The clip can be ordered separately (part #4200-R-LEVER) and is easily replaced. Most refurbished or third party fusers I’ve seen have the new style clip but every once in a while I still run into the old style. So they are still out there and should be replaced if you see one.
Black Swing Plate Gear
The most common noise issue in this HP Laser Jet printer series is with the black gear on the swing plate assembly.
Originally HP thought that by adding a spacer to the swing plate assembly all of their problems would be fixed. But, as time goes on, it’s becoming obvious that the problem is related to the intense pressure applied to the fuser assembly and the speed at which the printer operates.
The problem is pretty easy to detect by removing the fuser and checking for gear dust in the cavity under the gears
or by checking the gears themselves for abnormal wear on the gear teeth. If you see a pile of black or tan dust or the teeth look extremely worn, the gears will need to be replaced. At first most techs were just replacing the swing plate gear [part # RM1-0043-KIT] but more and more are now recommending that the swing plate and fuser pressure gear [part # 5851-2766] be replaced together at the same time, which is what I typically do if not replacing the fuser. The reasoning is that both the gears wear abnormally together so by just replacing one the other will wear the new gear down prematurely.
I’ve tried just replacing the swing plate gear a few times lately to see what the outcome would be and on several occasions found that, while making the machine work and reducing the noise, the machine still ran louder than usual or had a light clicking noise in the rear until the fuser pressure gear was replaced.
The black swing gear and spacerr [part # RM1-0043-KIT ] can be purchased separate of the whole swing plate assembly and can easily be replaced by removing the formatter assembly.
Behind the assembly, in a hole in the middle of the metal frame, is a black or silver screw, screwed into the shaft that the black gears sits on.
Carefully unscrew the screw and remove the metal shaft inside the cavity of the machine. As I said before, be careful as the metal shaft can fall out and drop down inside the machine and become unreachable. While you have the shaft out check it to make sure that it hasn’t worn grooves in it. If it has done so then replacement of the whole swing plate assembly [part #RM1-0043] will be needed as the shaft isn’t sold separately. I usually keep an extra swing plate assembly with me so I can just remove the shaft from the new assembly without replacement of the whole unit.
Reinstallation is a little harder than removal. I usually line the gear and spacer up with the hole, insert something small, like a canned air straw, through the formatter side, put the shaft on it after its fed through the gear and spacer then push the shaft through using the straw as a guide and to support the shaft to keep it from falling. Screw in the shaft, reinstall the formatter, switch out the fuser pressure roller gear and you should be good to go.
I have a few hundred of the 4200, 4240, and 4250 models in the field. Some never have an issue and on others I have replaced the gears from once to several times, and on a very few the whole assembly. So while some of these models may never give you an issue some might always wear more than the others. What the difference is I cannot say. I will say, that at least on the few printers that I have had to replace the gears several times, the gears usually wear out every 100,000 to 150,000 prints so you do get some life out of them between replacement.
The M4345 and 4345 series copiers take the same parts but are a lot more difficult to replace. I would strongly advice finding someone with lots of experience to perform this repair as it is quite labor intensive just to replace the black swing plate gear.
Another thing that can cause noise is a broken pressure roller gear [part # RC1-3324].
Many times the gear looks good on the outside but if you remove it you will notice that around the gear shaft they can crack. If you have a noise problem that you can’t quite figure out you might want to remove this gear and check out the inside for extreme wear. I’ve seen them look great on the outside but totally broke inside to where the gear doesn’t even drive the pressure roller and no sound is noticeable.
In rare cases on machines that have gone through a few black swing gears, and have high print counts, the main white swing plate gear wears out. It’s pretty easy to notice when you replace the black gear and fuser gear and the machine is still giving you issues. Visually inspect with a flashlight when the black gear is out. The whole swing plate is inexpensive and removable but hard to replace as a lot of the machine needs to be torn apart. Find step by step instructions here.
In the HP Laser Jet 4200, if you have smeared print on the sides of the page, then most likely the fuser film is torn. When this printer was first introduced the film tore quite often due to one of the flanges in the fuser. The part has been updated over the years so that problem is fixed but tears still happen more often in this model than on most HP printers with the film technology.
If you get a call for a 4200 with poor print quality on the side and pieces coming out the back expect to replace the fuser [part # RM1-0013 ]. On the other models the film is actually metal inside, which is more durable; an upgrade HP felt necessary to have with the speed of the machine. However, I’ve seen on several occasions the film to be slightly sluggish and not move at the same speed as the pressure roller resulting in smeared print, or what most customers call blurred print, because it usually comes out legible but for some reason just doesn’t look right. In extreme cases the film ceases to move at all resulting in paper jams as the paper hits the fuser.
Ghosting and Repetitive Defects
In models with metal in the fusers more repetitive defects and ghosting can occur. Previously, because there was no metal in the film, when the film got damaged it would tear. With metal film in the fusers, they can take more of a beating but it leads to more image defects.
I’ve seen on several occasions when the machines get around 175,000 to 200,000 prints the top coating of the fuser wears out and the metal gets exposed in the middle of the fuser. Toner builds up on the spot and ghosting starts to appear.
Also, with the toughness of the film, creases in the film can result leaving repetitive defects across the pages and noise in the fuser area. Again, with the old style, frequently when the film would crease the material would kind-of bounce back out to its original form. With the new style once the metal is creased it’s creased for good.
Ghosting still occurs around the edges like in previous models. If you notice this ghosting, pull out the fuser and look for discoloration around the edges. Again, usually this will start happening around 175,000 to 200,000 prints and on some fusers no discoloration is noticeable. The fuser and toner cartridge rollers are about the same in diameter so troubleshooting can be a little more difficult. If in doubt do a Half Test: Print off a config page and when the paper is half way through the machine open the top cover and remove the toner. If the defect happens before the paper hits the fuser then replace the toner [part # Q1338A for the 4200, Q5942X for the 4250 and 4350, Q1339A for the 4300]. If you don’t see any defect before the image is fused then replace the fuser [part # RM1-0013 for the 4200, RM1-1082 for models 4240/4250/4350, and RM1-0101 for the 4300].
Creases in the middle of the page
Fusers usually get blamed for this problem but over the past few I’ve come to pay more attention to the paper used. On HP Laser Jet 4200 and 4300 printer model series whenever I get intermittent creases in paper I always focus on the paper and try a few different paper types before I commit to replacing the fuser. Interestingly, this problem seems to happen most once summer gets into full swing when the humidity is high. Several times I have found that the customer had recently switched paper types to save money, so ask questions.
Alright, that’s all I have to say about the fusers. Yeah, it’s a lot of information to take in on such a small assembly. But by far it’s the most important part of the machine and takes most of the load. The one nice thing is that the fusers for these HP Laser Jet printers are relatively cheap and very easy to replace. So the worse case scenario is replacement, but given the cost of the machine and the value it has in everyday business operation, customers typically have no problem deciding to fix the machine.
Kevin Gumpp is a certified printer technician and freelance writer for Market Point. If you have a question for Kevin regarding this topic or have any other printer repair related questions or topics you would like more information on, please send an email to firstname.lastname@example.org.