Lexmark T640 -- Developer Drive Access/Overhaul

A machine that's had a serious toner-fouling incident will likely need to have its developer drive assembly removed, cleaned, lubricated and reinstalled. Following is the access procedure and the teardown/overhaul procedure specific to a T640. All prior 'S' and 'T' series machines are very similar. Machines with separate engine-controller/formatter architectures won't confront you with a mass of cables to be unplugged as the T640 does.

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1) Left Side Cover
> Two finger-operable claws at the front. Swing it open far enough and its upper hinge will pop apart harmlessly for removal.

2) System PCA Enclosure Cover
> Loosen off six M3x6mm pan head screws.
> Slide the cover forward slightly and pull it away over the screw heads.

3) System PCA w/Enclosure
> Twenty or twenty-one cable connections, depending on model.
> There may be a ty-wrap to be cut on one of the printhead cables.
> Free the cabling from the enclosure's cable openings.
> One M3x15mm hex washerhead screw at the PCA's upper rear corner.
> Three M3x10mm washerhead threading screws. They're near the PCA's three other corners.
> The item is free to come away from the chassis.

NOTE: Before proceeding, observe the interaction of the developer drive assembly's pivoting cartridge engagement lever, and the plastic lever that's linked to the access door's hinge. Note that the engagement lever is inboard of the plastic lever.

4) Developer Drive Assembly
> One M3x28mm pan head screw at the lowermost position.
> Two M3x8mm pan head threading screws.
> The item is free to come away. NOTE that there is a loose drive coupling hub, along with a clip-fit drive coupler, between the developer drive and the main drive. NOTE their relationship.

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Proceed as follows to dismantle the developer drive assembly:

1) Loose Drive Coupling Hub

2) Clip-Fit Drive Coupler

3) Lever Return Spring

4) Lever
> One e-clip.
> Withdraw the pivot pin upward.

5) Triaxial Self-Aligning Coupler
> One e-clip.
> One flat washer.
> Coupler body.
> Spring.
> Gear w/drive spline.

6) Large Idler Gear
> One e-clip.

The remaining gear is a snap-fit item that's best not removed.

Clean all components with Varsol in a parts washer.

Lubricate the gear spindles with WD-40 on reassembly.

Lubricate the coupler's flat washer and e-clip area with light mineral oil. Do not use grease anywhere.

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