Something is bugging me. Please help.

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  • BillyCarpenter
    Field Supervisor

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    • Aug 2020
    • 16331

    #1

    Something is bugging me. Please help.

    Let me say this upfront. This information is only to satisfy my curiosity. It's not a necessity to repair a copier but I'd like to know. Back in the day, I started in the business working for a Sharp dealer. That's where I was taught the basic copy process (analog) and later the digital copy process. I clearly remember one of the main differences being that the polarity for the drum and DV voltage was opposite from the analog machines. That's been a long time ago and it's foggy in my mind.


    Anyway, when I started training the new guy, I wanted to be accurate when describing the copy process and include the correct drum and DV charge voltage. You may want to call it "bias" voltage but you know what I'm talking about.

    Anyway, nowhere in the manual can I find any information of this. Oh, I can find what board produces the voltages to the mag roller and PCR and the control signals for each but that's about it.

    I'd like to know is the mag and PCR voltage negative or positive? And what are these voltages?

    Lastly, what is the polarity of the developer? (If the dv has a positive polarity, then the toner will have a negative polarity. Correct?)


    Do they still teach any of this or no?
    Adversity temporarily visits a strong man but stays with the weak for a lifetime.
  • bsm2
    IT Manager

    25,000+ Posts
    • Feb 2008
    • 29988

    #2
    Re: Something is bugging me. Please help.

    Kyocera services manuel will go into detail on the copy process. Kyocera usually hides the voltages in specification page or not listed at all.

    Most of the settings are DFW do not F with and are digital.

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    • Copier Addict
      Aging Tech

      Site Contributor
      10,000+ Posts
      • Jul 2013
      • 14563

      #3
      Re: Something is bugging me. Please help.

      Both the drum and the dev carry the same charge to start. Usually between -600 and -700 volts. The printhead then writes the image on the drum, thus causing the image portion of the charged drum to carry a different voltage. The charged toner is then attracted to the portion of the drum with the different charge.

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      • bsm2
        IT Manager

        25,000+ Posts
        • Feb 2008
        • 29988

        #4
        Re: Something is bugging me. Please help.

        OmG

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        • BillyCarpenter
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          • Aug 2020
          • 16331

          #5
          Re: Something is bugging me. Please help.

          Originally posted by copier addict
          Both the drum and the dev carry the same charge to start. Usually between -600 and -700 volts. The printhead then writes the image on the drum, thus causing the image portion of the charged drum to carry a different voltage. The charged toner is then attracted to the portion of the drum with the different charge.
          Hhhmm....

          I think the voltage is negative but there's no printhead. There's a laser and it writes a latent image on the drum that is less negative (the voltage isn't positive, it's just more positive where the laser hits on the drum) thus the toner is transferred only to the part of the drum that the laser touched.

          I know the complete theory of how it works, I simply need the voltages and the polarity.
          Adversity temporarily visits a strong man but stays with the weak for a lifetime.

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          • BillyCarpenter
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            • Aug 2020
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            #6
            Re: Something is bugging me. Please help.

            By the way, I'm pretty sure the voltages change as more pages accumulate on the DV's and DR's. The voltages increase via calibration to compensate for wear & tear. Same with laser intensity and exposure lamp. Correct me if I'm wrong.
            Adversity temporarily visits a strong man but stays with the weak for a lifetime.

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            • Copier Addict
              Aging Tech

              Site Contributor
              10,000+ Posts
              • Jul 2013
              • 14563

              #7
              Re: Something is bugging me. Please help.

              Originally posted by BillyCarpenter
              Hhhmm....

              I think the voltage is negative but there's no printhead. There's a laser and it writes a latent image on the drum that is less negative (the voltage isn't positive, it's just more positive where the laser hits on the drum) thus the toner is transferred only to the part of the drum that the laser touched.

              I know the complete theory of how it works, I simply need the voltages and the polarity.
              Printhead, laser, write unit, LSU, same thing.

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              • PrintWhisperer
                Trusted Tech

                250+ Posts
                • Feb 2018
                • 467

                #8
                Re: Something is bugging me. Please help.

                I think the best way of thinking about it is to leave polarity out of it. It really doesn't matter.

                Best to think of the drum surface and 'Charged' or 'Discharged'.

                For Kyocera Charged areas repel toner. Drums are uniformly charged until hit (written) with light (LSU) causing them to discharge (Ground potential=0) creating the latent image (latent as in unseen and consisting of differing charged areas)

                Discharged areas attract toner, hence the phrase 'Write to Black'

                This whole positive/negative perspective can change with manufacturers technology. You could use opposite charged toner and 'write to white' instead, which is how analog machines worked.

                As for DV, it is usually an AC bias which fluctuates between being 'more positive and less positive' compared to the drum potential in order to have a 'push/pull' effect where the actual 'duty cycle' pushing toner is determined by offsetting the 0 point of the AC sine wave with an additional DC bias (slice level)

                That's an early days Canon description but it still applies.
                "Being ignorant is not so much a shame, as being unwilling to learn" - Benjamin Franklin

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                • BillyCarpenter
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                  #9
                  Re: Something is bugging me. Please help.

                  Originally posted by copier addict
                  Printhead, laser, write unit, LSU, same thing.

                  Wasn't trying to nitpik. I just never heard a laser called a printhead.
                  Adversity temporarily visits a strong man but stays with the weak for a lifetime.

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                  • BillyCarpenter
                    Field Supervisor

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                    • 16331

                    #10
                    Re: Something is bugging me. Please help.

                    Originally posted by PrintWhisperer
                    I think the best way of thinking about it is to leave polarity out of it. It really doesn't matter.

                    Best to think of the drum surface and 'Charged' or 'Discharged'.

                    For Kyocera Charged areas repel toner. Drums are uniformly charged until hit (written) with light (LSU) causing them to discharge (Ground potential=0) creating the latent image (latent as in unseen and consisting of differing charged areas)

                    Discharged areas attract toner, hence the phrase 'Write to Black'


                    This whole positive/negative perspective can change with manufacturers technology. You could use opposite charged toner and 'write to white' instead, which is how analog machines worked.

                    As for DV, it is usually an AC bias which fluctuates between being 'more positive and less positive' compared to the drum potential in order to have a 'push/pull' effect where the actual 'duty cycle' pushing toner is determined by offsetting the 0 point of the AC sine wave with an additional DC bias (slice level)

                    That's an early days Canon description but it still applies.

                    That pretty much answers my question. I need to know these things.
                    Adversity temporarily visits a strong man but stays with the weak for a lifetime.

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                    • tsbservice
                      Field tech

                      Site Contributor
                      5,000+ Posts
                      • May 2007
                      • 7986

                      #11
                      Re: Something is bugging me. Please help.

                      Originally posted by BillyCarpenter
                      Wasn't trying to nitpik. I just never heard a laser called a printhead.
                      This is KonMin terminology...and maybe some more brands. Btw here is a link to one good animated training about copy process with few quizzes.
                      WeSendit - Swiss File Transfer Service
                      A tree is known by its fruit, a man by his deeds. A good deed is never lost, he who sows courtesy, reaps friendship, and he who plants kindness gathers love.
                      Blessed are they who can laugh at themselves, for they shall never cease to be amused.

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                      • slimslob
                        Retired

                        Site Contributor
                        25,000+ Posts
                        • May 2013
                        • 37397

                        #12
                        Re: Something is bugging me. Please help.

                        Originally posted by BillyCarpenter
                        Let me say this upfront. This information is only to satisfy my curiosity. It's not a necessity to repair a copier but I'd like to know. Back in the day, I started in the business working for a Sharp dealer. That's where I was taught the basic copy process (analog) and later the digital copy process. I clearly remember one of the main differences being that the polarity for the drum and DV voltage was opposite from the analog machines. That's been a long time ago and it's foggy in my mind.


                        Anyway, when I started training the new guy, I wanted to be accurate when describing the copy process and include the correct drum and DV charge voltage. You may want to call it "bias" voltage but you know what I'm talking about.

                        Anyway, nowhere in the manual can I find any information of this. Oh, I can find what board produces the voltages to the mag roller and PCR and the control signals for each but that's about it.

                        I'd like to know is the mag and PCR voltage negative or positive? And what are these voltages?

                        Lastly, what is the polarity of the developer? (If the dv has a positive polarity, then the toner will have a negative polarity. Correct?)


                        Do they still teach any of this or no?
                        In the very old days of coated paper fluid developed analog only the paper was charged after passing through the corona. There was no bias supply for the developer. Reflected light from the original burned the charge off except where the text and images were and the toner was drawn to the latent charge. The same was also true of most early plain paper analog copiers, except since plain paper did not hold much charge, they had to add a chargeable intermediate where the image was created and then transferred to the paper. Many of those initially used "masters" that had to be replaced frequently. They then need 2 HV supplies, 1 for charging the master and a second fro transferring. Some like the RBC II used a roll of master material that the copier automatically advanced after a fixed number of copies. Then coated drums were finally introduced which could produce many times more copies before they started to deteriorate. Depending on the type of drum, the charge polarity was different.

                        In some of the early Ricoh laser service manuals they had a Detailed Description section that went into the entire process including voltages needed from the HVPS.

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                        • Phil B.
                          Field Supervisor

                          10,000+ Posts
                          • Jul 2016
                          • 22798

                          #13
                          Re: Something is bugging me. Please help.

                          Originally posted by tsbservice
                          This is KonMin terminology...and maybe some more brands. Btw here is a link to one good animated training about copy process with few quizzes.
                          WeSendit - Swiss File Transfer Service
                          IBM/Lexmark is another that calls them a printhead.

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                          • tsbservice
                            Field tech

                            Site Contributor
                            5,000+ Posts
                            • May 2007
                            • 7986

                            #14
                            Re: Something is bugging me. Please help.

                            Originally posted by Phil B.
                            IBM/Lexmark is another that calls them a printhead.
                            Hey Phil, Thank you brother
                            A tree is known by its fruit, a man by his deeds. A good deed is never lost, he who sows courtesy, reaps friendship, and he who plants kindness gathers love.
                            Blessed are they who can laugh at themselves, for they shall never cease to be amused.

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                            • BillyCarpenter
                              Field Supervisor

                              Site Contributor
                              VIP Subscriber
                              10,000+ Posts
                              • Aug 2020
                              • 16331

                              #15
                              Re: Something is bugging me. Please help.

                              Originally posted by tsbservice
                              This is KonMin terminology...and maybe some more brands. Btw here is a link to one good animated training about copy process with few quizzes.
                              WeSendit - Swiss File Transfer Service


                              I'm forever in your debt. That is excellent. And again, thanks for telling me that KonMin calls the laser a printhead. I've only heard of a printhead in inkjet printers. Learn something new every day.


                              I'll also add that PrintWhisper is spot on. It really doesn't matter about the polarity of the charge roller because it changes from one manufacturer to the other and will be determined by the charge of the toner/carrier.


                              Thanks to everyone that responded.
                              Last edited by BillyCarpenter; 12-11-2022, 08:38 PM.
                              Adversity temporarily visits a strong man but stays with the weak for a lifetime.

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