Drum repair (Z+)

Drum repair (Z+)
Difficulty	Expert
Duration	½–3 hours
For series	Z+Any machine released with or after the RZ line, i.e. RZ/RV/EZ/EV/SF/SE and MZ/ME/MF/MH machines.
Tools	JIS phillips #2 screwdriver 4 in (100 mm) zip ties Clear packing tape Doublestick tape Solvent Isopropyl alcohol Gloves Rags

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1. How to: clean an MZ/EZ/RZ drum to change colors

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There are many reasons a drum may need to be opened—to repair an issue, clean out old ink, transition to a new color, etc. This article outlines the common processes in disassembly, testing/cleaning, and reassembly, but does not go into specific maintenance (i.e. correcting the squeegee gap, replacing the squeegee gear, etc.)—those are separated out into their own tutorials.

The golden rule of drum repair is: only go as far as necessary, and no further.

Drum repair is inherently dangerous to the riso.

• Misassembling a drum and trying to print with it can result in totalling the drum and damaging the riso itself.
• Many of the individual components in the drum are quite delicate.
• The process is arduous and messy, and it's easy to make mistakes when fatigued or working alone (ask for help).

Doing as little as possible on drums is a good way of limiting the potential for error.

Evaluation

Before opening a drum it's important to create a plan of attack—to determine how much disassembly is required. A lot of assessment can be done before opening up a drum—both how it is functioning mechanically, and electrically.

The first step of any drum work is to test the mechanical components with a "drum safety test."

Drum safety test (Z+)

The drum safety test is a quick test of the most critical mechanisms in the drum. It is used to evaluate if it is safe to insert the drum in the riso. This test should be performed:

• Before and after doing any maintenance on a drum.
• On drums of unknown status (used drums, drums which have been shipped, or not used in a while, or might have suffered damage).
• On any drums which are behaving strangely (regularly printing weird, making strange noises, etc.).

If a drum fails any of the parts of this test it should not be run in the riso until it can be repaired.

The drum safety test is most easily performed on the drum while it is sitting in the rails of the risograph (but not pushed into it). Remove the stencil by hand before performing this test.

① — Clamp

The tolerances inside the riso are very small (~1 mm for the separator needle and <5 mm for other sensors and components), and the drum is spinning very quickly—so anything protruding too high off the surface of the drum is in danger of getting caught in the riso. The clamp is already the part of the drum which protrudes the most—so anything wrong with the clamp can result in catastrophic failure.

1. The clamp should easily flip open when pressing the orange clamp lever, and snap closed when released.
2. The master ejection bar should lift up easily by hand and snap back down when released. Check that the ejection bar sits flat against the drum, and is not bowed out in the middle.
3. Check for the presence of two rounded metal clips near the center of the clamp (they can fall out, or become bent/mangled).
4. Check the two white wheels and white peg at the end of the clamp—the wheels should be unbroken and spin freely; the shafts they are mounted on should be parallel with the axis of the drum (not crooked).
5. Check that all 4 screws are in the clamp.

② — Screen

The drum screen is attached via two bars in the ends of the screen—each of which is attached at the front and rear of the drum. Anytime a tensioned surface is only attached in the corners like this, the bars will bow up slightly in the middle—it's important to make sure that the bars are not bowed up so high that they will catch on the separator needle.

6. The heavier bar (2 screws) should not raise higher than the surface of the metal lip of the clamp assembly next to it. Check it in the middle by dragging a finger tip from the surface of the screen mesh onto the clamp assembly—there should be a distinct step up to the clamp.
7. The thinner bar (4 screws), with the rubber strip along the edge, should not raise higher than the surface of the ejection bar next to it. Again, check in the middle, by dragging a finger tip from the surface of the rubber strip onto the ejection bar—there should be a distinct step up to the ejection bar.
8. Check that all 6 screws are in the screen, and that there is no damage to the screen bars.
9. Check around the screen for signs of major tears—if the mesh separates too high, it can also get caught in the riso.

③ — Rotation

When the drum is inserted into the riso, its rotation is unlocked, so that it can be spun during operation. When spinning, a series of internal rollers are engaged, which help distribute ink along the length of the drum. If the ink is very old/oxidized it can glue the rollers together, then when the riso tries to spin the drum it will either break the gearing inside the drum, or overload the main motor in the riso.

10. Click the manual unlock button (small round button at around 2:00 along the front blue/grey plastic flange) in and out a few times, it should move freely and snap back into the locked position when released.
11. Rotate the drum slowly in the print direction (counterclockwise) while holding down the unlock button. The drum should spin easily, and sound smooth during the whole rotation process. It can be compared to the feeling of rotating a working drum by hand. If the drum can only spin in the opposite direction (clockwise) it is a sure sign that the rollers are glued together by old ink and need internal cleaning (the rollers only engage when spinning in the printing direction).
12. While rotating the drum check for any major dents in the drum body—small dents won't cause additional damage, but heavy dents can deform the drum body enough that it can collide with the insides of the riso.

④ — Ink

Lastly, check for signs of separated ink. This can appear as an oily residue on the surface of the drum body (usually underneath the drum when it's in the locked position), inside the ink tube holder, in the ink tube itself, or even in the drum case. If a drum has heavily separated ink in it, it's quite likely it needs an internal cleaning before it will ink properly, and that it might be heading toward more issues.

It's also important not to use separated ink tubes in drums, as this will cause further issues with them. Instead, separated ink should be remixed before use.

If a drum fails any of the parts of this test it should not be run in the riso until it can be repaired.

Access port

Most of the internal components of the drum can't be easily accessed without disassembling it, however there is a display window through which much of the key mechanism can at least be seen.

Removing the ink tube from the drum, there is a small plastic panel inside, along the bottom of that channel—it can be clicked out, much like the battery cover on a remote control. Shining a light in here will expose the inner rollers and the ink and overflow sensors.

• Is there ink built up on the rollers? The most extreme overflows will cause ink to build up high enough to be stuck onto the ceiling of this chamber, and make contact with the circuit board.
• Is there not enough ink on the rollers, are they dry?
  • The largest roller, the squeegee roller (which forms the "floor" of this chamber) should have a thin coating of ink along the length.
  • The medium-sized roller to the left, the doctor roller, should be mostly clean of ink.
  • The smallest roller (the ink driving shaft), which sits between them, should always be encased in a bead of ink, no smaller than the line of toothpaste that would come from squeezing a toothpaste tube. This bead of ink is the reservoir of ink inside the drum.
• How is the quality of the ink? It should more or less look like the ink does when pressed directly from the ink tube. If the ink looks dry (dull matte finish), or there are chunks of sediment in the ink, it's likely that it has separated in the drum and the drum/rollers may need cleaning.
• Find the two ink sensors and make note of if they are touching the reservoir (the bead of ink around the ink driving shaft). The sensors are two needles which extend from the green circuit board at the top left, at an angle just below horizontal.
  • The longer needle is the ink sensor, if it is touching the ink reservoir the riso will not pump anymore ink into the drum.
  • The shorter needle is the overflow sensor, if it is touching the ink reservoir the riso will throw an ink overflow error and stop printing.
  • Ink on the end of the needles does not affect the sensors, they only detect if the needle is touching the reservoir itself (the sensors complete a circuit through the conductive ink and rollers).
  • If ink has built up at the base of the needles, where they connect to the circuit board, they may misfire.

If it is safe to rotate the drum in the riso (it has passed the § Drum safety test), it can be turned once without a tube in, using test mode 892. Looking into this window while the drum rotates can give a sense of how the ink is moving inside the drum: the bead of ink should roll clockwise, while the squeegee roller rotates counterclockwise beneath it.

The drum should not be rotated too many times without an ink tube in, as this can cause the riso to try pump ink, filling the pump with air instead, and locking it up.

Electrical evaluation

Using test mode, many of the electrical components in a drum can be tested without fully disassembling it. Additional electrical tests can be completed with the drum disassembled (described in a later section).

The following table outlines the components and the unit tests for them.

Test mode	Component	Description	Causes for failure
811	Ink cartridge set switch	This test should read ONFast beeps and an analog display of <code>╷╷╷╷</code>. when the ink tube is clicked in, and OFFSlow beeps and an analog display of <code>oooo</code>. with no tube. This is a good test to run first, to evaluate if the drum is connecting with the riso at all.	Drum not fully connected/clicked in. Broken plastic "fin" on the ink tube. Cartridge set switch unplugged (blue connector inside the body of the drum).
809	Ink sensor	The longer sensor needle, which detects the ink in the reservoir. If the longer needle is touching the ink in the reservoir it should read ON, and OFF if not. If it is not detecting, the riso will try to pump ink whenever the drum is spinning (assuming there is an ink tube which is recognized and has not been marked as empty).	Ink buildup on the ink sensor PCB has short circuited the needle. Ink sensor improperly installed, and stuck between the ink driving shaft and the doctor roller. Ink sensor unplugged.
810	Overflow sensor	The shorter sensor needle, which detects if the ink in the reservoir has built up too high. If the shorter needle is touching the ink in the reservoir it should read ON, and OFF if not. If it is detecting the riso will throw a T/P04-513 error—the "ink overflow" error and stop printing.	Ink buildup on the ink sensor PCB has short circuited the needle. Ink sensor unplugged.
882	Inking motor	This test will run the ink pump motor when activated—which can be heard as a high pitched whirring inside the drum. This test should only run for a split second, or ink can build up inside the drum (as drum is not spinning during the test). Some models of riso will automatically end the test after 0.5 seconds, but others will not. If the test runs longer than 1 second, immediately hit STOP to end the test.	If there is no motor sound, the ink pump motor may be unplugged, or the motor itself may be failing. If a T/P24-539 error is thrown, but the motor is running (high pitched whirr was heard), then the ink pump encoder disk sensor is likely unplugged or failing.
1211 (protected areaThe protected area test modes are accessed by first running test mode <code>9874</code>.)	Drum memory	This test reads the first four digits of the drum serial number from the memory stored on the drum PCB. It can be used to evaluate if the riso can read the drum memory on the drum PCB. It should be performed with the front door closed (to make sure the riso has locked the drum in place). The value should be a positive number (and correspond with the first half of the 8-digit serial number printed near the back handle of the drum).	If the value is 0, one of the other components may be unplugged inside the drum (the riso blocks access to the drum's memory in this case). If the value is -1, it's likely the memory for the drum has not been set, has been reset, or has become corrupted.
Failure of the drum PCB, drawer connector, or wire harnesses—or the drum PCB being unplugged—are possible causes of misfiring of all of the above components—and have not been included in the "causes for failure" listings. The above tests do not account for: issues with the RFID reader or antenna (which recognizes the ink tube) or the actual values in the drum's memory.

This article should probably be split up into at least two additional articles. One for the drum safety test (Z+) and another for common drum issues. They will unfortunately be dependent on this article for the disassembly process—but many of the other tutorials probably will be too.

Common drum issues

Combining: (1) observations of the issues the drum has been having during operation, (2) the mechanical safety test, and (3) the electrical component test—can reliably diagnose most drum problems. And once the problem is identified, the technician can determine what sort of repair is necessary, again minimizing disassembly as much as possible.

The following charts describe the most common drum issues, their possible causes, and how much disassembly they require.

The stages of disassembly in the following instructions are underlined and refer to the step by step process in the next section, § Disassembly procedure.

Inking issues

Issue	Behavior	Cause(s)	Procedure
Ink overflow	The riso throws a T/P04-513 error message and refuses to print with this drum.	Ink has built up inside the drum to the point that it is contacting the shorter ink-overflow needle, but is not yet in contact with the ceiling of the chamber visible through the viewing portal (see § Portal access above).	Disassembly may not be required, instead, the excess ink can be "printed out". With full-width scrap paper in the tray, run test mode 80 to make a checkerboard (mask off the front 2" if the paper sticks to the drum). Print out the old ink with test mode 888 (ink drainage action) until the printed image is very faded. Run test mode 887 (inking action) to re-ink the drum.
		Ink has built up so high in the drum that it is in contact with the ceiling of the reservoir chamber and/or ink sensor PCB.	The drum needs to be disassembled through to accessing the rollers, and cleared out from this point. The squeegee gap should also be checked/calibrated at this time.
		See ink overflow for more information about this issue.
Drum not inking	Even with multiple inking, printing, and cleaning attempts, no ink is coming through the drum.	The pump is filled with air, and is not successfully pulling ink from the tube (this is very common in brand new drums).	Disassembly may not be required, instead the pump needs some help being primed with fresh ink. Ensure that the riso accepts the ink tube with no errors (or else it may reject the tube and not attempt to pump ink). Run test mode 887 (inking action) while pressing in lightly (more force than would be required to crush a grape, but less than it takes to puncture an orange) on the plunger in the back of the ink tube. Feel for the riso beginning to pull the plunger in under its own power—when this happens, the pump is primed and should be working normally.
		The ink sensor is reading ON even with no ink in the drum (see § Electrical evaluation above)—thus the riso falsely believes that there is already ink in the drum, and thus is not pumping any additional ink.	Disassemble through Removing the ink sensor to ensure that the ink sensor (long needle) is properly positioned, and there is no ink buildup on the ink sensor PCB. If there were no clear issues, proceed to the internal electrical test to confirm the ink sensor is working properly.
		The ink pump motor has failed (see § Electrical evaluation above), so the riso is trying to pull ink, but the pump is not actually running. In this case the riso is likely throwing a T/P24-539 error.	First check all the connections with the drum PCB, to make sure the ink pump motor is not merely unplugged in the front of the drum. If this is not enough, disassemble through removing the drum body and make sure the ink pump motor and encoder sensor are properly plugged in inside the drum. If necessary, proceed through separating the ink pump & motor to the internal electrical test to test the ink pump motor in isolation.
		The ink pump is clogged (or has a bad seal/gasket)—the riso is running the pump but no ink is being pulled.	Be sure to try the previous instructions a pump filled with air first. If that fails, disassemble through separating the ink pump & motor, then run the "mechanical test of the ink pump" described in that section. The pump may need internal cleaning, in the taking apart the pump stage.
		The nozzles or internal plumbing of the ink distributor may be clogged—usually this looks like the drum inking well in one or two stripes side-to-side (parallel to the axis of the paper feed), but remaining dry in the other areas.	Disassemble through removing the drum body, then clean the nozzles of the ink distributor with solvent. It may be necessary to continue through separating the ink pump & motor, so that the "mechanical test of the ink distributor" can be performed.
		The squeegee roller is not rotating, so ink is not being distributed along the length of the drum. This appears often as thin inked lines at each of the four nozzles, but no other inking. It is very hard to distinguish this from a dry screen/drum body—it can only really be determined by watching the squeegee roller fail to rotate while looking through the viewing portal (see § Portal access above).	In this case, it's most likely that the one-way bearing in the squeegee gear on roller has failed. If the gear itself has broken, there may be a distinct clicking sound as the drum rotates. Either way, it must be replaced (see replacing the squeegee gear for instructions).
		See inking mechanism for more information on how the internal inking process works. If repeated problems seem to be occurring with the internal rollers, the squeegee gap may need to be calibrated.
Ink leakage	Ink is seeping out from underneath the clamp and/or to the left of it.	The adhesive seal on the ink blocking sheet (part of the ink recycling mechanism) has failed, and ink is leaking through it during printing.	Disassemble through removing the screen, then follow instructions for reattaching the ink blocking sheet.
False empty ink tube error	The riso is registering an ink tube as empty even when it still has ink—eventually it will refuse to print with this tube.	The riso tried to pull ink for a set period of time, but did not detect ink in the drum even after that time. This will throw a C01-512 error.	Remove the tube and click it back in. Optionally run test mode 887 (inking action) to try and re-ink the drum. It can be useful to increase the values of drum test modes 943, 944, and 946 (if available) to increase the amount of inking time in the future (multiple the current value by 1.5 for 50% longer inking time).
		The riso has permanently marked this tube as empty (on the tube's RFID sticker), throwing a C01-574. This is a common and known issue for Z+Any machine released with or after the RZ line, i.e. RZ/RV/EZ/EV/SF/SE and MZ/ME/MF/MH machines. drums—so long as the ink tube carries this RFID sticker, the riso will refuse to print with it.	Replace the RFID sticker on the tube with a "blank chip." This will generate an H01 error any time this drum is used, and the ink parameters will need to be put in by hand.
		If this is continually an issue with this drum, it's likely the ink pump is failing (either the motor has weakened, or the vacuum in the pump is poor, so not enough ink is being pulled).	Disassemble through separating the ink pump & motor, so that the "mechanical test of the ink pump" can be performed.
		See false empty ink tube error for more information about this issue.
Debris in the rollers	A sharp white line (wider than a single dead pixel runs along the length of the print (parallel to the axis of the paper feed), and is also visible running around the drum.	Some debris or corrosion is stuck between the squeegee and doctor rollers, so ink cannot reach that area.	Disassemble to accessing the rollers, then use a feeler gauge to scrape out the debris. Turn the back flange by hand afterwards to ensure the gap is now inking properly on the squeegee roller.

Press issues

Issue	Behavior	Cause(s)	Procedure
Dry/patchy drum	A printed image is coming through, but it is very patchy.	If the drum has not been used for a while, it is likely that the screen or drum body is clogged. Three soft, three wide light bars running from side-to-side (parallel the axis of the paper feed), or a thin line corresponding to the bottom of the drum body in the resting position are the two areas most likely to dry first.	Remove the stencil manually, then wipe the surface of the screen with some solvent on a rag (following proper solvent safety). If this improves, but does not resolve the issue, disassemble through removing the screen, then clean both sides of the screen and the surface of the drum body with solvent.
		If the front and rear edges of the printed image are patchy, on all drums (but perhaps some more than others) the most likely cause is the buildup of dry ink on the pressure roller, not an internal drum issue.	Clean the pressure roller.
		See inking mechanism for more information on how the internal inking process works.
Separator needle scratch	An ink mark or scratch is appearing around the clamp/screen in the center of the drum.	The separator needle is running too close to the drum and scratching the surface of the drum. This can be a very dangerous issue—the drum may soon be punctured by the separator needle.	If this is happening to only this drum, there is some issue in the installation of the clamp or tension in the screen. Disassemble through removing the screen then reassemble. If this is happening to all drums the separator needle needs to be recalibrated (see separator calibration for instructions).
Drum body deformation	A thumping sound is happening while printing with this drum. When turning the drum by hand, a lower squelch can be heard consistently at a specific angle of rotation.	The drum body either has a dent, or was installed without proper tension and is raised up in some areas. This sound is the ink between the squeegee roller and the inside of the drum body separating and coming back together as the bumped out area passes the squeegee roller. A small sound will often be heard when the clamp passes the squeegee roller—this is expected behavior; this issue is specifically referring to a louder sound at any other angle.	Disassemble through removing the drum body, then reinstall—making sure to get the drum body back on in proper tension. The drum can be rotated by hand after taping the drum body closed again, to check for how it sounds.