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Russell H.
Russell H., Service Tech.
Category: Office Equipment
Satisfied Customers: 11046
Experience:  10 yrs fixing office equipment. Decades of typewriter fixes.
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I have a Konica Bizhub c360 with P-9 and P-21 error and no

Customer Question

I have a Konica Bizhub c360 with P-9 and P-21 error and no black, All of the drum units are new, the back I just replaced and no change. the black has been intermittently light for a while now but seems to be completely gone at the moment. Could there be a problem in the toner hopper?
Submitted: 1 year ago.
Category: Office Equipment
Expert:  Russell H. replied 1 year ago.

Hi, thank you for contacting My name is Russell. I will do my best to provide the right answer to your question.

If the P-9 and P-21 errors appear on the computer's screen, then you have a problem with the server certificate, perhaps, according to what listings I have on K-M c360 errors. Certificate errors can sometimes happen because one or another machine is set to the wrong date (e.g. wrong year but right day and month can do it) - or if all machines are set alike, but the source for their setting is not accurate.

If that is an accurate interpretation of the error codes you cite, if those errors are on the computer not on the printer's screen itself (and they should be), then you must treat the toner problems altogether separately.

What replacements have been made in the printer lately? and when was the last drum replacement for black ? print going faint and then away altogether, unless the drum is conspicuously new, can often be from steady usage of the black drum by text printing.

So if the black drum is definitely not new, and if text printing has been a fairly predominant use of this printer, I would suspect the black drum has gone bad. (But until confirmed, if you try replacing the black drum, save the 'old' black drum in the new one's packaging, in case it is still good and can be re-used.)

Customer: replied 1 year ago.
Hello, Russell, The error codes are viewed from the display panel on the machine - no network issues that I am aware of. In the information I posted with my question there was information on what steps I have done. I have replaced the black toner (the old toner tube looked completely empty although the screen still said that I had some left. I did a manual load toner under service mode adjustments, after this I had good black for a few days then it faded out again. I then changed the black drum, but this has had no effect on the output. The counter is at 87,000 black pages, about 170k total. The developer unit is the only other piece I can see to replace but it is supposed to last 500k copies (at least the black one). Before I replace the developer I would like to know what else may cause this problem, the service manual does not have much detail on what can cause the problem only that there is some kind of failure of the drum/developer. I am not sure how it knows if toner supply is reaching the developer or if there is a problem with the motor that turns the developer.
Expert:  Russell H. replied 1 year ago.

I researched the error codes, and found they are listed as meaning

Black Drum or Developer Unit Failure


Color Registration Test Pattern Failure.

Which I understand to mean that print is not being produced in black, basically, and that it is *not* a toner failure or toner supply failure.

The old toner tube may have looked empty because all the toner had gone down the tube but has not quite been exhausted in the workings of the print system that actually use toner.

When drum or developer are listed as problems, then I would say you need to try replacing one or the other.

To find out whether the motor is turning the developer? observe whether there's a distinct ridge of toner deposted upon the developer film in one location along the film's loop - without damaging the developer film by exposure to light or touching it! which would definitely require that the developer be replaced. You wouldn't have to turn the developer film to see it - it should be right there, if toner is being supplied to the developer but none is being used nor scattered along the developer by the developer being turned.

Customer: replied 1 year ago.
Hello Russell, I will order a new developer unit, it will probably take a day or two to get here and see if this solves the problem. I did pull the developer unit yesterday and it looked like there was an even distribution of toner. I will let you know if this solves the problem. If it is the problem I am curious as to what would cause the premature failure of the unit at only 1/4 of the expected lifetime.
Expert:  Russell H. replied 1 year ago.

When you look at the inside of the printer, is there any loose toner or spilled toner in the works anywhere?

That might cause apparent or real failure of the developer.

Expert:  Russell H. replied 1 year ago.

Also exposing the developer to light a lot, or (forbid!) scrubbing it or wiping it, might cause failure.

Customer: replied 1 year ago.
Hello Russell, Given that the failure was intermittent at first I don't think it is likely the developer unit was damaged by light exposure or by physical contact as I would expect this to have a constant or deteriorating effect. Since I removed and re-installed the developer unit last night, it is possible that it is now damage as well. There was very little excess toner in the machine when we first noticed the problem, and none of it was black.
Expert:  Russell H. replied 1 year ago.

If you didn't keep the developer in the direct bright light for over 1 (60-second) minute, and if you didn't touch the developer film, then it isn't damaged I doubt.

But if the problem is intermittent, it might be quite expensive: the power supply or high voltage power supply, perhaps. An intermittent problem is likely one that is owing to poor contacts in the printer.

Have you tried the printer since you took the developer out to examine it? does it still show error messages? can it do a test print?

Customer: replied 1 year ago.
Hello Russell, there has been no change since I removed and re-installed the developer, but this does not tell us much as we are not getting any black images now. I would have expected a power supply problem to have an effect on all colors not just black. A contact is possible but also unlikely as we have seen a deterioration over time (we first noticed the problem with faded black then faded to faint black, then back to normal etc. until this past week when it faded out to the point there is no visible black printed. I have ordered a developer unit so when it gets here I will see if it has any effect.
Expert:  Russell H. replied 1 year ago.

Is the developer unit for the black only?

Or is it for all colors?

If for all colors, then since other colors print, it cannot be the developer. (We should have thought of that first... but I apologize for myself.)

If the developer is common to all colors, but the problem is only in the black color, then the problem must be the drum (mounting, for instance, or dirt on contacts, etc.) or some other black-section-only problem.

Try removing, briefly examining the area where it fits for loose toner, debris, anything broken... then replace, properly, the black color drum.

And see if that helps, or brings back the black printing, at all.

Customer: replied 1 year ago.
Hello Russell, there is a separate developer unit for each color so it is possible that there is a fault in the black developer unit, I will know tomorrow assuming the new part arrives on time. Since I installed a new drum after the problem started and it had no effect, I doubt there is a problem with the seating. I have to remove the drum again to install the developer so I will do a thorough cleaning but I do not suspect this is the problem.
Expert:  Russell H. replied 1 year ago.

OK. Let's see how it goes, then, being well-prepared. Let me know how it goes, and get back to me at your convenience. Thanks.

Customer: replied 1 year ago.
Hello Russell, I replaced the developer unit. I got some black but it quickly faded after a couple of test prints. There is one error code, we now have error P-5 which seems to indicate a problem with the IDC (Front) sensor. Perhaps this has been the problem all the time. I presume there is some way to clean the sensor, but I am not sure even where it is located, I think it may be behind a shutter that is supposed to protect it from getting dirty. If you have any ideas on what may be wrong, or if you think it is the IDC sensor, any ideas on if it can be cleaned and how?
Expert:  Russell H. replied 1 year ago.

If it's an optical sensor, cleaning it means finding it and wiping it with a clean dry rag cloth.

If it's some other kind of sensor, 'cleaning' would only mean picking debris or paper scraps off of it or out of it.

IDC means Image Density Control. There are usually two of them, near the transfer belt.

Vaccuuming dust off them, after removing the drums, developer, and transfer belt, is usual.

I have as yet been unable to locate an illustration of the position of the IDC Front sensor.

Customer: replied 1 year ago.
Hello Russell, I just checked the error display again, it now show P-9 again, and no P-5. The description for this is "All density readings taken from the density pattern pro-duced on the transfer belt are 1.0 g/m2(IDC sensorphoto receiver output) or less during max. densityadjustment (Vg/Vdc adjustment)." or "All density readings taken from the density pattern ro-duced on the transfer belt are 5.0 g/m2 (IDC sensorphoto receiver output) and more during max. densityadjustment (Vg/ Vdc adjustment)." - Since we know the drum and developer are good (both have now been replaced) perhaps it is still a sensor problem.
Expert:  Russell H. replied 1 year ago.

Perhaps so.

But the density sensors are still at issue, whether the fault code is P-5 or P-9.