Something is bugging me. Please help.

[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?

[bsm2]

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.

[Copier Addict]

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.

[bsm2]

Re: Something is bugging me. Please help.

OmG

[BillyCarpenter]

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.

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.

[BillyCarpenter]

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.

[Copier Addict]

Re: Something is bugging me. Please help.

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.

[PrintWhisperer]

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.

[BillyCarpenter]

Re: Something is bugging me. Please help.

Printhead, laser, write unit, LSU, same thing.

Wasn't trying to nitpik. I just never heard a laser called a printhead.

[BillyCarpenter]

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.

That pretty much answers my question. I need to know these things.

[tsbservice]

Re: Something is bugging me. Please help.

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

[slimslob]

Re: 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?

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.

[Phil B.]

Re: Something is bugging me. Please help.

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.

[tsbservice]

Re: Something is bugging me. Please help.

IBM/Lexmark is another that calls them a printhead.

Hey Phil, Thank you brother

[BillyCarpenter]

Re: Something is bugging me. Please help.

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.