Phaser 840 loud buzzing.

[petervideo]

Hi,
My 840 is making a loud buzzing noise after the print job ends. The printing is OK and there are no error messages.
I removed the cover and observed that the motor driving the print drum is oscillating causing the noise. Is this fault caused by the motor or the supply. (Or anything else??)

Any help would be much appreciated.

 

[Dacurve]

The tension of the y-axis belt is (probably) not high enough, which drives the drum. On the 840 you will need the y-axis belt tensioner to tighten it again (seperate tool, part# 003-1500-00)
Even better would be to fit the y-axis tensioner of the phaser 850/860, which fits on the 840 frame as well (650-4148-00).



Removing/Installing Belt (phaser 850,860 -----> follow this if you fit the tensioner of these machines on your 840)
1. Remove the right cover.

2. Disconnect the wiring harness leading from the front panel to the right

I/O board passing beside the Y-axis belt drive assembly.

3. Remove the drum fan. (Note the fan orientation, it blows into the drum.)

Caution Never loosen or remove the three screws securing the assembly

parts together. Also, improperly removing the tension spring can

cause the tension bracket to flip off forcefully, causing injury.

4. Insert a flat-blade screwdriver through the tension bracket as a .holder.. Anchor the

screwdriver tip against the Y-axis belt drive assembly.

5. Remove the tension bracket.s mounting screw. Using the screwdriver as a lever,

slowly tilt the bracket up and away from the frame.

6. Remove the three mounting screws securing the Y-axis belt drive assembly to the

engine frame. Remove the assembly with its two belts.

7. Reverse these steps to reinstall the Y-axis drive assembly.

8. Tension the belts using the "Y-axis belts tension adjustment (Phaser 850/860 printer)",



Adjusting tension:



1. Ensure that the three mounting screws that secure the Y-axis drive assembly to the

chassis are 1 turn loose and that the Y-axis drive assembly slides freely with respect to

the chassis.

Note If there is a situation in which diagnostics are not available when

installing a new Y-axis drive assembly or drum/transfix assembly,

then locate any previously placed index marks on the pulleys and

proceed as if re-using existing parts. Allow the system to cool as

long as feasible before mounting the Y-axis drive assembly onto

the chassis. Tensioning of the y-axis drive assembly without

diagnostics increases the risk of failures associated with low belt

tension (for example, a .growling. sound heard upon cold

power-ups).

2. If not in place, attach the tension spring between the Y-axis drive assembly and the

tension spring bracket.

Note A metal clip attaches the spring to the Y-axis drive assembly; the

spring DOES NOT attach directly to the plastic housing of the

Y-axis drive assembly. Refer to the illustration on page 7-201.

3. While the belts are under tension, rotate the drum pulley 5 times to rotate the belts and

seat them in place. For an old Y-axis drive assembly, continue rotating the pulleys until

the index marks on each pulley align next to each other.

4. Beginning with the upper-right screw, tighten the three mounting screws to 30 in.-lbs.

to secure the Y-axis drive assembly in place.

5. For new Y-axis drive assembly (Phaser 850). Using PC-based diagnostics, run the

test: .Position for Belt Tightening. in the .Y-Axis Group. test suite. This positions

the belts in the proper orientation for re-tensioning. Do not move the pulleys.

For the Phaser 860. Use the adjustment from the service menus.

6. Place an index mark on the edge of each pulley: Mark the Y-axis drive pulley and the

drum pulley where the edges are closest to one another, disregarding previous marks.

Use a distinct color if the pulleys have been previously marked.

7. Loosen the 3 mounting screws until the bracket slides freely on the chassis and then

re-tighten the screws to 30 in.-lbs.

8. Reassemble the printer and make a test print.

 

[petervideo]

Thanks Dacurve for your quick reply.
The fault is not the belt jumping teeth. The drum motor is actually oscillating about 15 degrees each way at about 25 htz. This happens momentarily before printing and for about 2-3 seconds justafter the last page of a print job completes.

 

[melhof]

The answer Dacurve did give was right.
The belt doesn't have to jump teeth before it needs retentioning. If it is, it is actually far to late.

The motor wants to set the drum still at a position after a print job. When the belt doesn't have enough tension the motor becomes instable to hold it at a position. After some time it stops trying. The oscillating noise is a sign for retentioning.

I also have a question my self.
Does anybody know how much force the belt tension tool puts on the Y-axis drive assembly?
Can you tension the belt with only a stack of papers (with certain weight) hanging on it over a pulley? (the pulley to get the force in the right direction)

Thanks,
Melchior

 

[marty5261]

Not sure what the tension is applied by the tension tool but you can try applying tension by either pulling back on the assy or using something as a lever to put tension on the belts as you rotate the drum to seat the belts then tighten them down. If not using a torque screwdriver be careful not to over tighten or break off teh screws by applying too much torque.