HP 42xx / 43xx short life fuser problems

[nvl51]

Looking for some input. I'm trying to determine the cause of short life failures on rebuilt fusers for the 42xx & 43xx series HP Laser jet printers. Typical failures are poor print quality (blurry print) & Paper jams in the fuser which occur mostly during large print jobs. HP claims that fusers should be replaced at 200,000 pages, most of the failures I have seen are occuring at 20,000 pages or less.
Originally I thought that it might be the type of grease being used in the fuser but have not been able to confirm this due to limited resources.

[Manuals]

There is a service note on the fusers on these machines. I have it posted on my site at http://www.manuals4you.com/free
You can also Google it.

HtH
Paul@justmanuals.com

[raz]

how short is the short life?i believe that originally there was a bushing problem with some of these fusers that were causing their life to be considerably shortened.this would usually cause the fixing sleeve to slide over to one side and tear,so if a kit was replaced,the bushing issue would still cause issues.otherwise , if there is no spacer with the swing plate;it could cause issues.

if someone is printing in a heavier or lighter mode than is needed on a consistant basis.it can cause issues.in what your saying,it sounds like something could be happening with the heating element and in some cases an issue with the low voltage power supply can also cause this type of thing.

i believe that there is 110v and 220v fusers for these models.have you tried to ohm out the affected fusers with a multimeter to test the resistance with the thermistor and heating element?

just a couple ideas anyway.

[MichaelTech]

The drive gear seems to wear out fast, even with the spacer in the swing plate. This is design by HP. All their products are engineered for failure before the rated lifetime.
The new fast units are being over-used and just not up to what a salesman tells you. People try to get production quality on something that is just not going to do it for long. Now, tech support with HP {har, har, har!} is starting to be a chargeable affair. I get better info here and at other sites I participate in. I can Google something faster, and get a better answer.
I/O problems are increasing, and F/W is shoddy. I am thinking of just promoting other products instead of HP. And I am service/ssales authorized on just about everything they make!

[ptjeff1]

First, the 4200 fusers have a plastic sleeve which is very prone to ripping, often under 50,000 pages. We have a modified version of the 4200 fuser that has a metal sleeve that pretty much eliminates that issue. Like MichaelTech said, HP uses numbers like the maintenance interval as a sales pitch. These models often don't make it to 200,000 pages before a maintenance kit is needed. Other manufacturers do the same so it's just a game they play.

This brings up the HP service notes. I personally think they are often just like political spin. HP makes a statement that is supposed to address the technical issue but it really does nothing. This was the case with the "flange angle" HP blamed on the 4200 sleeves ripping, and the service note Manuals mentions describing moving the Fixing Cross Member (attached to the power board) all of about 1mm or less. That's about how much play there is in the screw holes if you make this adjustment. Also, the pivot gear is spring loaded and the gear on the 4250 fuser is spring loaded, so there is a bit of cushioning in this gear meshing, AND there is play in the way the fuser clips into the frame. Try this--with the fuser properly installed, you can rotate and move the fuser forward and backward about .5mm. With all of this play in they way the fuser is clipped into place, is moving the fuser back and down less than 1mm by adjusting the cross member really going to change anything? I think not. Adjusting the cross member doesn't really pull the fuser back away from the pivot gear since the gear is designed to pivot into the fuser gear, hence the name. At best you are changing the angle that the fuser gear makes contact with the pivot gear, and a very very slight angle at that. In the short-term this should wear on the teeth differently but not eliminate wearing. Eventually you will still need to replace the swing plate gear. I would guess that with the speed of these printers and the amount of slop in how the fuser fits in place, you really can’t completely correct for the swing plate gear wearing. The good news is that it doesn’t take long to replace the swing plate gear, the black gear, but if you need to change the entire assembly—woe is you, you have a big project. [As a side note, if you are changing the swing plate gear and spacer with aftermarket versions we have found them to wear much faster than the OEM. They seem to leave a powdery residue which causes even more friction and wear.]


You mentioned grease. This I'm sure many people rebuilding these fusers aren't using a grease with a high enough temperature rating. I've heard that the grease HP uses is Nye Uniflor 8172, although I can't confirm this. The problem with this is that the 8172 is only rated to 225 C. The Laserjet 4250 operates at 230 C. You are already out of the recommended range of that grease. If the grease breaks down too soon the sleeve might have a harder time rotating and then you could get smeared print or paper jams. We use a grease with a higher temperature rating.

If you often get jams during large print jobs this might not always be a fuser problem but a feed problem. We would need the error code on the display to further determine the cause. If you had a jam at the front of the printer, this would cause the printer to stop, and the preceding sheet could be in the fuser at this point. So it could look like a fuser jam but really be a feed or pickup issue.

So if you are blowing through fusers at 20,000 pages this is far too soon. Without having more detailed info it's hard to say what the problem is, but in generally the 42x0 and 43x0 aren't quite as robust as the 4000 & 4050 printers.

[MichaelTech]

Ah....the thought plickens. Yes, the "adjustment" angle is actually a viable issue. The Power supply assy. can be set a little lower than it should be, resulting in the fuser not being positioned correctly. This results in undue wear on the fuser drive gear. As I said, the plastic is different in the fuser gear, and the swing plate gear. Again, this is an HP design for purpose:selling parts! The new breed of printers are very intolerant of component positioning.
That 1mm does make a difference, so when re-assembling, pay attention to alignment of parts when setting the screws. HP has a lot of dirty litle secrets, and their ambiguous "support" is just a sham. Credit the "engineers" who's fault-based designs are the standard for their products. If they will not give us what we want, we should give someone else our business. But, then again, Who?