Troubleshooting Problems in the HP LaserJet 8100 and 8150

I know The HP LaserJet 8100 and 8150 printers are older models and it may seem like they are past their prime, but I still have several out in the field and recently I’ve seen a resurgence in service calls for these models. In this post I’ll share some of the more common problems with these printers in an attempt to help you diagnose and repair them as needed.

50.1 Fuser Error in the HP 8100 and 8150
You’re probably thinking “how hard can the 50.1 fuser error be to fix?” In this model, like the old HP LaserJet II and III series, the error is usually related to the AC power supply, not the fuser. Actually, about 90% percent of the time it’s the AC power module. When servicing machines for this error I typically pull the fuser out and check the thermal fuse on top of the fuser and the lamps inside the unit for continuity to verify the problem isn’t in the fuser. I also check that when the machine turns on it doesn’t initialize and then say “warming up” on the display.  If it just jumps to 50.1 error, that is another give away.

After verifying the problem is related to the AC power supply I check the fuser for common wear and tear in case the fuser also needs to be replaced. When checking the fuser:

  • Check the middle of the hot roller for toner build up that could cause ghosting or poor print quality.
  • Check the pressure roller and gears for signs of wear.
  • Check the bushing by rotating the gears on the side of the unit. The gears should rotate smoothly.

If the bushings are worn I typically notice:  (1) Metal shavings that fall out as I’m checking the unit, and (2) a jerky feeling as I rotate the gears. If you experience any of the above issues with the fuser then I recommend quoting the fuser replacement along with your quote on the new power supply.

Power Supply Removal in the HP 8100 and 8150

AC Access Cover
1. Remove the Formatter PCA
2. Remove 3 screws

Back Cover
Note: Remove the metal back cover and the plastic panel at the right side rear cover as a single unit. The square opening at the upper rear corner on the right side plastic panel is the engine test access.
HP 8100 and 8150 50.1 Fuser Error Power Supply Removal Instruction    HP 8100 and 8150 50.1 Fuser Error Power Supply Removal Instruction    HP 8100 and 8150 50.1 Fuser Error Power Supply Removal Instruction

1. Remove 5 screws
2. Open the top cover door, and remove 2 screw
3. Open the 2000-sheet input tray transfer door (if installed), tray 1, and the right lower door assembly
4. Remove the 2 screws from the plastic panel to the left of the metal back cover
5. Carefully release the cover around the AC input connector at the lower right of the back cover and slide the right side of the cover slightly forward
6. Carefully release the retaining tabs on the plastic panel to the left of the metal back cover by gently pulling the cover to the left while moving both pieces away from the printer chassis

Fan 3, Formatter Fan
Fan Housing
Remove 2 screws and remove housing.

 Low Voltage Power Supply
1. Unplug 3 LVPS connectors
2. Unplug the LVPS fan (FM1) cable from the DC Controller
3. Remove 7 screws

Note: Make sure you remove the LVPS fan from the unit and put it on the new one before installing back in your machine.
HP 8100 and 8150 50.1 Fuser Error Power Supply Removal Instruction

Paper Registration Issues on the HP 8100 and 8150
Customers typically will say the image is being cut off on one side of the page or they will say the image is shifted. Several things can cause this issue. Here’s how to troubleshoot:
1. Determine if it’s happening from all the trays or just a specific tray.
2. Print a configuration page and make sure the paper size settings match what you have in the tray.

If the registration problem is happening from just one tray then we can troubleshoot just that tray.
The main problem I see with individual trays is the top or bottom of the page being cut off. If this is the case for your situation then check your tray’s blue paper guides to verify the guides are snug against the sides of the paper. Some users release the paper guides to install new paper and then forget to move them back and lock them in place. This can cause print skew and or the top and bottom of the image being cut off because it’s not centered in the tray.

Second thing is making sure the paper guides are in the right position. I see this situation most often in industrial locations where you have employees who don’t understand the value of the equipment they are using and don’t handle it properly. Instead of releasing the lock mechanism they move them individually by force, which breaks the teeth in the bottom of the tray, causes the guides to no longer be centered in the tray, or they no longer fit the paper snuggly when pushed together. The guides might look normal but they don’t match up with the paper size marks on the metal lift plate in the tray. If this is the case or if when pushed together the guides don’t fit the paper snuggly then you will have to remove the metal lift plate.

Adjusting the Paper Guides in the Tray
Note: Before you remove the lift plate make a mark in the bottom of the tray that coincides with the mark on the lift plate so when you align the guides you have something to use as a home position.
HP 8100 and 8150 Adjusting the Paper Guides in the Tray

1. Remove the metal lift tray
2. Remove the screw in the center that holds the two guides in place
3. Position one of the guides in place with the mark that you put on the bottom of the tray
4. Insert a few sheets of paper and adjust the other guide snug against it
5. Remove the paper without moving the guides
6. Reinstall the center piece and the metal plate

If the image is shifted to the left or right and in all the trays then you probably have a registration problem with your registration assembly clutch.
As the paper feeds up into the machine the paper stops briefly at the registration assembly and creates a little buckle to make sure the paper is straight as it feeds through the image process portion of the machine. When the clutch fails, instead of stopping briefly at the registration assembly it keeps feeding through, causing the image to shift on the paper and part of it to be cut off. This problem usually starts off as intermittent or the first page prints fine and every other page has the defect. If this is the case you probably will have to replace the registration assembly.

Registration Assembly Removal

Transfer Roller Assembly
CAUTION: Handle the transfer roller from the ends only. Do not touch the surface of the transfer roller. Skin oils will affect its electrical characteristics, resulting in poor image transfer.
HP 8100 and 8150 Registration Assembly Removal

1. Open the top cover door and remove the toner cartridge.
2. Grasp the gear on the left end and carefully lift upward – just enough to clear the retainer clip.
3. Slide the transfer roller assembly to the left to release the shaft on the right end.

Registration Assembly
1. Remove the main gear train shield. Release the retainer clip and lift the forward end up.
2. Remove 2 screws at rear of assembly.
3. Unplug the clutch cable from the clutch on the right end of the registration assembly.
4. Lift the registration guide and remove 2 screws at the front of the assembly.

Paper Jam in the Right Side of the Machine Just Before the Registration Assembly
As the printer ages the feed rollers in the top of the Paper Input Unit (PIU) get a glaze on them or they start to wear causing the paper from tray 3 (or the 2,000 sheet tray) to have problems feeding through that area. Unlike tray 2, these are the only feed rollers pulling the paper through from tray 3.

When I am on-site to service a printer with jams in this area I always first test to see if tray 2 works while the other trays do not. When that’s the case, I check the feed rollers in the tray. If they look OK then the registration assembly will probably have to be removed. See instructions above.

The feed rollers are located under the jam plate just before the registration assembly — four black rollers on a long shaft the width of the feed path — hard to miss. I typically use alcohol or Simple Green to remove the glaze and restore the rubber on the rollers. If they look really bad and the machine has over 500,000 prints then replacement of the PIU should be done at this time as it is rated for 500,000 prints.

Paper Jam in the Left Side of the Machine with a Duplexer Installed
I’ve only seen this problem a few times but I’ve seen it enough on other forums and websites that I thought I would take the time to briefly talk about in this post. This problem is kind of an unexplained mystery for which nobody has a definite answer.  The majority of the time replacing the fuser fixes the problem. I believe it’s an internal power struggle between the fuser and duplexer. As the fuser ages the lamps tend to draw more power to get them to their correct operating temperature, similar to the issue now being witnessed in the P4015 models processing problem. As a result, not enough power seems to be getting to the duplexer resulting in paper jams. The best way to troubleshoot is to remove the duplexer and see if the problem goes away. If it does, replace the fuser.

Note: Lamps that are still working are not typically replaced in rebuilt fusers. In this instance I would recommend purchasing a new fuser rather than a refurb unit. I’ve heard of  instances where a refurb fuser was installed only to have to be replaced with a new fuser before the problem was truly fixed.

Conclusion about Troubleshooting the HP Laserjet 8100 and 8150
I have a lot of 8100 and 8150’s in the field that have well over 1,000,000 prints on them. These machines are great and can handle just about any type of paper, unlike their replacement model the 9000 and 9050 machines. The 9000’s and 9050’s can be touchy when handling any type of paper other than plain letter. Hopefully, this post will help you resolve some of the more tricky problems you’ll encounter with these machines to keep them running for a while longer. With the parts being so cheap now and the toner cartridges having such high yields they are well worth the repair investment.


Kevin Gumpp is a certified printer technician and freelance writer for Market Point. Photos courtesy of Bill Raymond, a certified printer technician at Market Point.  If you have a question regarding this topic or have any other printer repair related questions or topics for which you would like more information, please send an email to

One thought on “Troubleshooting Problems in the HP LaserJet 8100 and 8150

  1. Hi the problem with my 8150dn, when I switch on the printer it starts for about 3-4 seconds then switches off, any suggestions as to the fault.




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