I have a KM bizhub c 451 black imaging unit that prints faintly. I have replaced the following parts, PC drum, PC charger and starter( developer), yet it is not printing solid black.

Have you tried the High Voltage board that supply the voltage to the print heads and ITB. could be the print head is fine biut not getting any power to fire the laser and write to the drum

Sir/Mam,
Have you had the developer and drum replaced recently, or does the screen say Replace PC Drum? There are certain house chores the copier does before "Ready to Copy" it is waiting for them to get done, so that equals "Please Wait". One big item is making sure the developer and toner are properly mixed inside the image unit underneath the drum or next to it depending on the series. Might want to have the developer replaced and drum/cleaning blade normally done all together, then run the F8 procedure/Developer Charge, and make sure the counters where cleared. Did you recently replace the drum and the developer if so did you clear the counters for the drum and developer, FIRST? IF not then the copier thinks the new drum and new developer are old. The copier works on the counters that is how it knows it got a new drum and developer. Get new developer and a new drum and have it installed correctly. Counters are clear before the unit is yanked out of the machine, then you remove the image unit/drum unit replace the developer/drum and cleaning blade. (DO NOT USE A VACUUM CLEANER WHEN REPLACING THE DEVELOPER static electricity can destroy the sensor located below the developer unit. Then reinstall and RUN F8/Developer Charge. Make sure the fax line and Ethernet cable is removed can't print anything until the F8 is run. Or you will start all over again with new developer and a new drum.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

The corona housing for the back drum need to be replaced. Get a new black image unit drum and developer units

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

Have you had the developer and drum replaced or does the screen say Replace PC Drum? There are certain house chores the copier does before "Ready to Copy" it is waiting for them to get done, so that equals "Please Wait". One big item is making sure the developer and toner are properly mixed inside the image unit underneath the drum. Might want to have the developer replaced and drum/cleaning blade normally done all together, then run the F8 procedure and make sure the counters where cleared. Did you recently replace the drum and the developer if so did you clear the counters for the drum and developer, FIRST? IF not then the copier thinks the new drum and new developer are old. The copier works on the counters that is how it knows it got a new drum and developer. Get new developer and a new drum and have it installed correctly. Counters are clear before the unit is yanked out of the machine, then you remove the image unit/drum unit replace the developer/drum and cleaning blade. (DO NOT USE A VACUUM CLEANER WHEN REPLACING THE DEVELOPER static electricity can destroy the sensor located below the developer unit. Then reinstall and RUN F8. Make sure the fax line and Ethernet cable is removed can't print anything until the F8 is run. Or you will start all over again with new developer and a new drum.

try this site for developer and drum as a start


Precision Roller Printer Toner Cartridges Parts and Supplies Office...

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

Does you machine say replace PC drum on the control panel if so need to have the drum developer replaced at the same time. The code is dealing with the image unit the drum is one part the developer section is the bottom part or the sensor at the bottom of the image unit is bad. If developer was replaced did that person use a vacuum clean if so then the static electricity from the vacuum clean destroyed the sensor. NEVER USE A VACUUM to remove old toner. Worse case the main board that the sensor feeds is bad. Also when (if the drum and developer where replace did that person clear the counter for developer and drum. Machine works on info from counters to set certain voltages on certain assy. If the counters are not cleared then the copier thinks there is old developer and old drum in the machine and sets voltages for those units when in reality there are new drum and developer . Also after the developer was replaced was the required F8 run. And no prints/fax or copies where made before the f8 was run. When replacing the developer and drum the fax line and the Ethernet cable need to be removed first even used F8 and counters are done in service mode.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

Open the side door and see a colored cylinder, that is the drum, but removing it will not be easy, you have to remove the image unit and then separate it into two parts: developer unit and clean unit, already once separated the unit will be easierremove the drum.

Note, remove the module from the front image

The drum counter must be reset by using the service mode. But that is not your bigger issue here. The drum section is part of the Imaging Unit. When you change the drum section you are also suppose to change the developer (starter) in the developer section. So when you reset the drum count this also "resets" the atdc (automatic toner density control) ratio which must be recalibrated using the F8 mode. The 2 are tied together. You can try doing F8 without replacing the developer but this is just asking for trouble. Just resetting the drum count will mean you have at least a 50% chance of getting a COF32 code which is an atdc sensor failure because of the ratio mis-match that will occur.
You either need to find Imaging Unit rebuilding instructions or have a service tech come out and take care of this properly.
Good Luck and Thank You for using Fixya.

This machine has more than one drum unit, its a color machine. You have three color and one black as well as 4 developer units. You need to know which one needs to be removed. Shut the machine down unplug it from the wall. The upper units are the drums, which should easily slide out. If I remember correctly you have to flip up a clip on the front of each drum unit first to slide the drum out.