HP LJ 4000 Repetitive Defect Question

I have a LaserJet 4000 with a repetitive defect measuring in at 2-15/16". From the Repetitive Defect Ruler on PrinterTechs.com, this distance indicates either the Tray Feed Roller, the Separation Roller, or the Fuser's Upper Hot Roller is at fault.

I've fed a sheet into the manual feed and turned off the printer when halfway in and there is no defect on the sheet (pre-fuser), but how do I know that I'm not bypassing a problem that may have been introduced by feeding paper from a tray (by using the manual feed)?

In other words, does my test confirm with certainty that the fuser is the problem?

Thanks in advance,
Dave

It is very easy to pull the fuser out of this printer. Inspecting it may show the problem if you do not have a spare to swap into it. The measurement of the repetitive marks usually points to the fuser, the other mentioned sources are rare. Before you pull it out let it cool a little while and make sure the power is turned off.

Al

Listen to Al.
I have worked on laser printers for a long long time. I have never ever seen repetitive marks put on a page by feed rollers. It just isn't going to happen.
Pull the fuser and look at the rollers. One of them is probably damaged.

The only other thing that I've seen that can cause repetitive marks is when something gets on the drum in the toner cartridge (like sticky from a label or recycled toner cartridges). But if you did the manual feed test, the only thing is the fuser.

since you did the half page test from the manual tray, why not do it from tray 2?

easy to take the fuser out. look at it.

p/u, feed and sep rollers dont mark the page unless toner has dumped down in the tray cavity. Physically look at the rollers. Do they look dirty?