HP LaserJet 40X0 -- Registration Assembly Characteristics

[NOTE: The following applies equally as well to the 4100.]

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Functionality

The registration assembly in the LaserJet 40X0 is misnamed, actually. The 'registration' roller is in constant mesh with the drivetrain, and has no control whatsoever over leading edge registration timing. The registration assembly is strictly a constant-mesh paper conveyor.

There's a lightly spring-loaded 'gate' that rides on the upper roller, and presents four 'barriers' to the leading edge of a sheet of paper just before it enters the rollers' pinch. The gate is there to correct skew. By colliding with the straight row of barriers prior to getting pinched by the rollers, a sheet's leading edge will enter the rollers' pinch in alignment with the rollers.

Maintenance/Failure Mechanisms

See this post regarding bronze sleeve bearing maintenance.

See this post regarding swollen rubber rollers.

Loose Rollers

Further to the rubber rollers, the rollers can lose their grip on their steel shaft, rendering them ineffectual. The two outermost rollers seem to be the most prone to that.

Pictured below are a good new assembly, and an old defective one with two loose rollers. Note that I was able to shove the loose rollers way over out of place.

Those two outermost rollers are completely free-turning on their shaft. Unless they're out of place like the one's pictured, visual inspection won't reveal the condition. You have to take the assembly out of the machine.

With the registration assembly out, fold back the spring-loaded flap to get the pinch rollers away from the rubber rollers; then it's easy to check whether any rubber rollers are loose.

The defect pictured was causing mysterious, crumply jams at the registration roller, when all appeared to be in order.

Registration Gate Barrier Wear

In the following photograph, a new registration assembly is perched on top of an old, worn one.

Note the registration gate barriers. The new barriers have square-cornered ends. The old barriers are worn away to an angle. That amount of wear would render the skew-correction function inoperative.

Part Numbers

A LaserJet 40X0 Registration Assembly is P/N is RG5-2652. There are no service replacement components available for the assembly.

The registration assembly for the LaserJet 4100 is very similar but not identical. Its P/N is RG5-5085. No service replacement components are available for it either.

The photograph below shows a distinguishing feature.

Above is the 40X0 part. Below is the 4100 part. Note the cut/punched raised portion of the flap near the left side end of the 4100 part. That provides clearance for a sensor toggle that's not present in the 40X0.

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