It’s time for a good two-sided adventure. When they’re working right, the duplex transports on the DCP700 and C75/J75 do a wonderful job moving paper. However, when something starts slipping and pages start jamming (often intermittently), it can lead to frustration for a technician—a major time-sink.
Having a clear understanding of all the moving parts and knowing what to replace is key to saving time when solving the problem. We’ll cover the many parts in the upper chute assembly, the pinch rolls on the lower chute and the idler pulleys and drive belt on the inner front wall of the main transport drawer.
We’ll concentrate on the DCP700/DCP700i/DCP770 and C75 / J75 models, though a lot of this information will prove similar for the Versant V80, V180.
Upper Chute Assembly
There are several areas with parts related to duplexing:
- Duplex lower chute (six pinch rollers with their springs)
- Drive motor assembly (motor, gears and drive coupling)
- Duplex upper chute assembly (drive gears, one-way drive pulleys, and six transport rollers with their associated bearings)
- Main transport drawer (idler pulleys and drive belt)
The lower chute assembly is the metal plate that drops down, allowing you to clear jams from the duplex area. The only parts on the lower chute of significance would be the six pinch roll assemblies (hard plastic) and their retaining springs, which maintain nip pressure. If you find the paper is skewing in the duplex, you want to check these pinch rolls to make sure they all spin easily enough—clean the plastic cradle bearings, check that they’re not out of round from wear and add a drop of silicon gear grease for lubrication. Also check that the tension springs are all providing similar pressure. If these pinch rollers don’t turn easily, they add a lot more stress on the whole drive train, so checking and oiling them is an important first step.
The duplex drive motor assembly (068K59340, sells for around $85) is seldom the actual cause of drive problems. The motor itself has a part number on the label, 127K52720, although that number is not actually valid.
The drive assembly’s coupling drives a matching coupling on the rear of a shaft on the left side of the duplex upper chute assembly. The drive shaft reaches all the way to the front of the unit. There, you’ll find a 22-toothed D-shaft drive gear, which mates up with a one-way drive gear/pulley (20T/24T) on the front end of the duplex out roller. This piece drives the duplex drive belt, which moves a series of one-way pulleys, to turn the rest of the duplex rollers on the upper chute assembly.
The upper chute assembly is mounted under the main transport drawer. The drive belt gets its tension from idler pulleys (some smooth, and some 24T), which are mounted on the inner front wall of the main transport drawer.
Most of the duplex problems stem from a combination of increasing friction due to dirt and wear of the pulleys and bearings, and the subsequent failure of the one-way clutches (pin-bearings) found in the drive gear/pulley and the three one-way pulleys. Getting to the duplex drive belt and upper chute assembly takes a little bit of work.
Removing the duplex drive belt and upper chute assembly:
- Pull the main transport drawer (transfer drawer) all the way out to the service position
- Remove the drawer front covers: left cover (three screws), fuser release cover (two screws), center cover (two screws), right cover (two screws) and drawer handle (two screws)
- Lift the fuser out
- Remove the second BTR assembly: disconnect a connector and a high-voltage lead, take off second BTR front cover (one screw) and then rock the unit towards the right to lift it out
- Remove the registration module: disconnect four connectors at front, remove two screws (one front left, one rear left) and remove the spring-loaded guide pin near the front end of left rail (three screws and rotate the spring/pin assembly), but be careful, as it’s spring loaded
- Remove two metal brackets inside the front wall of main drawer: left bracket (three screws) and central bracket (two screws)
- Remove the duplex drive belt tension pulley bracket (one screw)
- Remove the duplex drive belt, taking careful note of how it is routed (see photo #1 for the layout, as viewed from the front end)
Duplex Upper Chute Assembly Orientation:
At this point, getting the upper chute assembly off is easy enough—here’s a quick anatomy.
The duplex in rollers (x2) on the right end of the assembly are driven by D-shaft pulleys, which don’t tend to wear out. The next three rollers, which we’ll call duplex transport rollers, are all driven by one-way drive pulleys. The one-way clutches in these pulleys can get weak over time and should be replaced if the duplex is slipping.
Similarly, the drive gear/pulley on the front of the duplex out roller (on the far left) also has a one-way bearing that can start slipping. All three one-way pulleys and the one-way drive gear/pulley should drive faithfully in the clockwise direction. If you suspect these are slipping, check the front ends of the shafts where these pulleys are seated. Look for signs of the metal getting worn out (discoloration and a change of texture), and replace any duplex rolls, if necessary. The wearing only tends to happen if the one-way pulley has already failed and is slipping on the shaft, so catch it early if possible.
You can replace the entire duplex upper chute assembly (054K35936, approximately $400) to keep things simple, or you might rebuild it with a duplex rebuild kit (DC700DXTRK, approximately $200). Once the upper chute is out of the machine, it’s straight-forward to rebuild (mostly a lot of e-clips). Below are some photos that show how the pieces should look when reassembled.
Duplex Upper Chute Assembly Bearing Layout:
Here’s a list of related parts, along with part numbers for the line items which are shown as spared on the OEM parts list:
Duplex parts you may need
- Duplex upper chute assembly (metal plate with six rollers, one-way pulleys and drive gears; 054K35936 or DC700DXUCA)
Retail cost approximately $400 for new OEM
Or, to rebuild the upper chute assembly
Duplex upper chute rebuild kit (includes all below):
- Duplex transport drive gear kit (DC700DXDGK) (one 20/24T one-way drive pulley/gear, one 22T D-shaft gear)
- Duplex in rollers (x2): (059K55960)
- Duplex transport rollers (x3): (059K54440)
- Duplex out roller (x1): (059K54430)
- Duplex roll bearing kit: (DC700DXBK) [oilite bearings (x10) (413W75959), tiny bearings for out roll (x2) and small bearings for drive shaft (x2)]
- Duplex drive pulley kit: (DC700DXPK) [one-way drive pulleys (x3) and D-shaft drive pulleys (x2) (499W14124)]
- Duplex upper chute rebuild kit: (DC700DXRK) (includes the drive gear kit, pulley kit, bearing kit, out roller and replacement tires for in rollers and transport rollers, as well as the drive belt and the idler pulleys described below)
When you replace or rebuild the duplex upper chute assembly, you’ll also want to replace the pieces on the transport drawer:
- Duplex idler pulleys (smooth) (x8): (499W17061)
- Duplex idler pulleys (24T) (x4): (499W14524)
- Duplex drive belt: (023E27010)
Note: there is also an idler pulley improvement kit, which has a set of smooth idler pulleys with a pair of ball bearings added to the centers of each. Item 655N00388 came with 7 idler pulleys, 14 flanged bearings and 14 white o-rings. There’s also item 655N00588, which only has 5 idler pulleys, 10 bearings and 10 o-rings.
That just about covers both sides of it all. Happy repairs, everyone—see you next time!
