Originally Posted by
lane1957
Hello Everyone! So, I have a customers HP M680dn CLJ that had a bad Main Drive Gear assembly making the usual grinding noises. I have replaced the main drive gear assembly. After reassembly, tried an engine test page print. I get no black line on the engine test page. Printed Configuration pages are completely blank. I have triple checked the main gear assembly alignment. Definitely not the problem source. Checked the lower HV board for spring contact alignment. All is good. So far I have changed out the lower HV PCB and DC Controller boards, and main formatter assembly, with known good boards. No change. Reinstalled latest firmware from a thumb drive. Using HP OEM toner cartridges and tried a couple of good black (K) cartridges. Still, no change. Checked to see if the OPC drum in the cartridge is moving during a test print. It does move. However, no toner is being applied to the black toner OPC drum. Used a multi-meter and checked all contact points from the new drive gear assembly to the HV board. All OHM out good. Used an Oscilloscope to watch DEV voltage generation to the black toner primary charging roller. Still nothing. No black toner is being applied to the OPC drum. Printer initializes perfectly with no error messages. All diagnostics via the Control Panel pass testing. Nothing in the event log except the usual half tone error codes regarding the black toner. I taped the toner cartridge contacts to see if I could get an all black page to print. Nothing...no change. Running out of ideas here. May be a faulty cable I suppose attached to the DC Controller board, or coming off of the HV board, but from the manuals I have been unable to determine how to check the signals with an Oscilloscope for the primary charge roller, or developing roller to see if there is a voltage or signal problem. Anyone have any ideas? Kind of complicated I know, but I am out of ideas....
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