Thermal-pressure motor lock (TPH Gear)

Thermal-pressure motor lock (TPH Gear)
Difficulty	Intermediate
Duration	90 min.
For series	RVEZEVSEMVMEMDMFMH
Tools	Phillips #2 screwdriver (magnetic) Flathead screwdriver Needlenose pliers
Parts	612-10010 1 × TPH Gear
Error codes	T19-XXX Thermal pressure motor lock !!System Error!!</br>Press Reset Key</br>If Recovery has Failed, Call Service

This is the draft of an article, it is incomplete or in-progress.

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This tutorial provides step-by-step instructions to replace a broken gear (part no. 612-10010 referred to colloquially as the "TPH gear") in the gear box for the thermal pressure motor—it's used in all Z+ type machines.

Overview

The thermal pressure system is used to keep the TPHThermal Print Head pressing the stencil material against the write roller, to ensure a clean image is burned. A great deal of force is put on this gearing, and this gear in particular will snap and shatter as the system wears. When it does, the riso will generate T19 or P19 errors and be unable to make a stencil and the whole machine will be locked in "call service" mode.

There is a known flaw in the manufacture of this gear, and the shaft system it sits on. While adjustments were made to the design of this area on some models, broken gears are still being found across multiple machines.

The part can be replaced, but it takes a little while to get enough access to remove it and swap the new one in—this is process is also slowed by the caution required when working with the TPH.

It's recommended that anyone running an RZ or newer machine have 1–2 replacement gears on hand. They are readily available on eBay and AliExpress by searching by the part number 612-10010.

Replacement procedure

The process of replacing this part is a little different between one- and two-drum machines (and depending on the make of your machine you may need to remove some additional covers to get access to things). It will take about 90 minutes the first time you do it (but can be done much more quickly once you know your way around).

Getting into the risograph

First, to access the sections we need, we'll need to pull the MMU (master making unit) out of the machine. Follow the steps you'd take to replace the stencil roll on your machine to get the MMU out (pushing the green button either to the right of the drum removal button on one-drum machines, or on the right side of the riso on two-drum machines).

Before you go any further, turn off and unplug the riso. From here on you'll exclusively be working on it unpowered—until the replacement is finished and everything is reassembled.

Accessing the pressure assembly

Replacing the gear requires access to the TPH pressure assembly, the gearing inside the panel with the TPH that is opened up when replacing the stencil roll. The method for getting into this area is different for one and two drum machines.

Removing the gearbox cover on one-drum machines

One-drum instructions

The steps in this section are for machines with one drum only.

The gearbox cover is a metal plate that sits just below the thermal printhead when the TPH is in the open position—usually it has an informational sticker on it explaining that the TPH can be hot and diagrams of how to clean it. It is removed with 4 M3×4 flange head phillips screws (with external hex profile).

• The first 2 screws are accessed with the TPH assembly in the closed/lowered position, from the left side of MMU—there is 1 at the front and 1 at the rear, near the hinges at the back of the assembly.
  1. Pull out the MMU if it is not already (the MMU can be manually unlocked if needed—but only if there is no drum sitting on the rails outside the machine).
  2. Remove the first 2 screws.
• The second 2 screws are accessed with the TPH assembly in the open/raised position.
  1. Open the TPH assembly by using the blue/green plastic handle that runs along the length of it.
  2. Remove the remaining 2 screws.
  3. Slowly remove the loose metal cover (make note that the lower lip of it sits beneath the two tabs that protrude on either side—this is what the first 2 screws were secured to).

Removing the gearbox cover on two-drum machines

Two-drum instructions

The steps in this section are for machines with two drums only.

The gearbox cover is attached in the same way on two-drum machines as on one-drum machines, with 4 screws in the TPH assembly. However on two-drum machines, because the MMU slides out of the side of the riso, instead of the front—the first 2 screws (those that are removed from the left with the TPH assembly closed) are inaccessible.

The official procedure in the service manual is to fully remove the MMU however, this is a complex operation that carries with it some risk. Removing and reinstalling the MMU involves manipulating delicate ribbon cables, checking parallelism on its rails, and handling one of the heaviest components in the risograph. There is another way to access the first 2 screws: sliding the MMU all the way to the left, removing the master disposal unit on the left side (a much simpler operation), and removing the screws through the opening that creates.

1. On the left side of the riso, above the paper feed tray, remove the master disposal box.
2. Remove the 5 screws that hold in the large plastic panel around the disposal unit and remove that panel.
3. Unplug the cables connecting to the disposal unit (generally there are two on the right side, depending on the model there may be a third on the left side), as well as any plastic cable guides that are holding the cables on the sides.
4. Tape the loose cables off to the sides so that they are out of the way.
5. Remove the 2 large M4×8 flange head phillips mounting screws in the top left and right corners of the unit.
6. Remove the 2 screws that hold in the plastic panel around the elevator lowering button and remove that panel.
7. The whole unit can now slide straight out of the riso (to the left, when facing the riso from the front/operator's position). Reach in and lift it slightly from inside the area where the disposal box goes, then pull it out.

• 

  The 5 marked screws secure the plastic panel around the disposal unit.

• 

  The two cables and small cable guide above them are marked in purple; the 2 screws holding the unit in are marked in green.

• 

  The paper feed cover is removed with 2 screws (it has two plastic arms at the top corners which hook over the metal shelf).

1. Reaching into the riso from the open door of the MMU area, on the right side, push the MMU all the way to the left side of the riso (first close/lower the TPH assembly if it is open/raised).
   • The MMU will be blocked at the beginning by a white plastic block at the rear of the MMU—this is normally pushed aside when the MMU door is closed—it can be bypassed by pressing in a small white lever at the rear hinge of the door by hand.
   • The MMU will naturally stop at the end of its track when pushed all the way to to the left.
2. Now the 2 gearbox cover screws (M3×4 flange head phillips screws) can be reached through the left—remove both of them (using a magnetic screwdriver so that they don't fall). If necessary, hold the MMU with one hand so it doesn't slide back to the right.

• 

  When pressed down, this small plastic hook will free the MMU to be pushed further into the riso.

• 

  Then press the MMU all the way in until it stops.

• 

  The 2 screws are on either end of a metal bracket on the MMU.

10. Reaching through the opening from the left, push the MMU back all the way to the right side of the riso (again, it will stop at the end) (the MMU can also be accessed through the openings for drums from the front of the riso).
11. Now pull the MMU out of the riso (as if replacing the stencil roll), and open up the TPH assembly with the green/blue handle.
12. Remove the remaining 2 screws (M3×4 flange head phillips screws) holding in the gearbox cover, and remove the cover.
    • These 2 screws are removed in the same way as in the one-drum machine instructions above.
    • Make note that the lower lip of it sits beneath the two tabs that protrude on either side—this is what the first 2 screws were secured to—when reassembling later, this plate will need to sit beneath the tabs again.

After finishing the TPH gear replacement, the master removal unit can be reinstalled by reversing the steps used to remove it.

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With the gearbox cover removed, the TPH gear is exposed—it's the bottom gear in the set—likely it will either be fully broken off the shaft or cracked. This is first true confirmation that the gear is in fact the cause of the T19/P19 errors, and needs to be replaced.

The rest of this process is documented in the old instructions below—it still needs to be cleaned up and rewritten for the new wiki. The images from the archived article will be integrated or re-illustrated.

Open and disassemble the MMU

9: Remove the TPH

• Avoid touching the TPH stripe (yellow/orange color).

10: Lift and remove the top bronze bearing metal.

• Remove the black plastic snap ring and spring, and carefully remove the bronze bearing

11: Unplug 2 cables connected to the TPH

12: Carefully lift the TPH while holding the lower bronze bearing metal

• Before you can fully remove the TPH, you need to unscrew the grounding wire (see next step).

13: Unscrew the grounding wire

• Hold the TPH and unscrew the grounding screw (green, used with an eyelet to safely direct electricity to the ground) , ensuring it does not fall inside the MMU.

14: Set the TPH aside for now

• !!! Be careful to not touch the orange strip !!!

15: Remove the top screws of the Thermal Pressure Gear Cover

• Unscrew the top 2 screws to remove the cover.

Inspect and replace the gear

16: Check the gear

• Inspect the gear for damage. If it is intact, the issue may be elsewhere. It should be fairly obvious that the gear is broken, as you will likely find broken parts at the bottom of the enclosure.
• If the gear is not broken, you likely have a different issue.

17: Remove springs from the fulcrum shaft

• The fulcrum shaft is the black horizontal shaft. It needs to be removed to access the broken gear.
• Remove the springs with care, as they are under tension.

18: Remove e-rings from both sides of the fulcrum shaft

• Be careful: e-rings are tight and can jump off. Use special e-ring pliers or a screwdriver.

19: Remove the fulcrum shaft

• Extract the shaft to access the gear.

20: Remove broken gear and related components

- Unscrew the white plastic piece and any remaining gear fragments. - Remove the tiny e-ring and push the shaft to the left.

21: Install the new gear

- Slide the new gear onto the shaft. - Reassemble the shaft and ensure the white plastic piece faces inward.

Put it back together

18: Reassemble =

- Grease the new gear and reassemble all components in reverse order.