March 2011, 220-702: 1.5 – Given a scenario, detect and resolve common printer issues

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Not corona wire *or* drum. Corona wires *and* drum.

The charge corona wire has a very high voltage applied to it which makes it give off a plasma (they glow purple) this ionises the air around it making ozone and in turn charges the surface of the photo-conductive material, the Drum.

Photo-conductive material is a semiconductor (it has been doped) which has a very interesting property, which is that it can be statically charged up and discharged in specific areas, with *light*. As happens with the exposure lamp and optics of a photocopier or the laser beam of a laser fax or laser printer

 

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I will add that is is becoming more common now to use a charge roller, this does the same job as a charge corona but gives off far less Ozone. Ozone (ionized air) is heavier than air and is not a good gas to have leaking into offices, so either you have to filter it out with ozone filters, or find an alternative method to charge your drum, hence the charge roller

 

Yes toner is a carbon based powder that has a plasticity which enables it to melt at a specific temperature, of the top of my head i would say around 180 deg C.

The fuser unit usually is comprised of two rollers, the upper being called the Hot Roller (in the uk) and is coated with teflon. The lower called the Pressure Roller, is coated with silicone. The rollers have heating lamps inside them and are under spring pressure, much like an old fashioned mangle.

This is why if the moisture content of the paper is too high (damp paper) the paper will dry out in the fuser unit and curl up, sometimes into a scroll. This can cause problems one of which of course is fuser jams.

 

Its way too late to be thinking clearly about printers...........but

just to touch on what soundaian said about memorising the Laser printer process as it is a very important topic from what I remember.......

This is Something which stuck in my mind from my A+ studying and has done to this present day in regards to how to remember the process.............

The Line

Curious Charlie Wrote Down the Facts

Clean, Charge, Write, Develop, Transfer, Fuse

 

I get your point. thank you..

Very good point. On the cleaning part it is very interesting how two cleaning process will take place as a over precussion to make sure the drum doesn't print the same image twice.

I think it is very importan to learn beyon, For instance What about if the blade that physically clean the drum toner left from previous image a double image would occur or maybe a the new image wouldn't get register. The other process. I think there is a static charge clean up before the image is draw in the drum. Have you heard about cleaning the static charged drum? why it would be necesary to clean up the static charged of the drum before drawing a new image in it?

Static Charged info taken from: http://www.scribd.com/doc/43390/Laser-Printer-6-Steps

From what I understand or imagine why the static charged would be necessary is becuase it could cause a paper jams, I think the static charged would leave the previous page in attached to the drum and then jam with the next one. What's your take on that?

I have seen some reference from bruce and bluerinse if I am not mistaken about some lights that take off the charge off the drum, but not sure wether you guys were refering about the cleaning process of something else.

 

Dunno why I put or I meant to put and.

 

a Great detail discovery channel instructing video where they literally take a apart a laser printer and just leave the drum, toner hopper, laser beam, toner rollers and the fuser.

http://www.youtube.com/watch?v=CFybx32Mvkw&feature=related

They have talked about how the paper is charged with positive electricity while another process takes place where the drum is charged with negative electricity and the laser beam draw an image into the negative charged drum by destroying each spot the laser hits in the drums by neutralizing (not negative or positive ) each spot in the drums is hit. Even though the video doesn't explain how the laser is created, how it is converted from the computer to the printer. I was also surprised it didn't explain the cleaning process in between previous and next page to be printed, I was expecting that part since I would like to know how the toner is removed and how the neutral spot in the drums from previous image drew are removed from it as well.

Then after those neutral spots are created in the drum a negative charged of electricity is adhere to each toner particles, this particles are transfer to a hopper roller, next to the drum with negative and neutral spots in it. The neutral spots are attracted to the negative toner particles sit on the hopper rollers. Those particles attract the negative toner particles adhering them to the drum. Now the drum has the neutral spots filled with toner, then the drums pass over the positive charge paper positive and negative attract to each other adhering the toner to the page and later fusing it at high temperatures so it permanently get in to the page.

i have also watch another video that doesn't quite explain the laser printer process in the same way. the video below says that as the paper roll through the drum it attracts the positive toner particle to the paper, while in the video above it say the opposite. The first video I showed you above say that the drums is charged with negative charges and adhere to the neutral spots in the drums. I guess the video below is considering neutral as positive, because instead of saying the drums filled with negative and neutral particles with toner adhere to the paper, it says the paper attracts the positive charged particle to it and then fused at high temperatures

http://www.youtube.com/watch?v=KtXes1sgUb4&feature=related

 

if you fllow the guide by soundian that is what you need to know about the lazer printing process for the A+. HAvea look at compTIA A+ all in one exam guide 7th edition by Mike Meyers it describes all you need to know about printers for the A+

 

This is why i have avoided discussing whether the charge on the drum etc are any particular polarity, because, it depends on the type of photo-conductor material that is used. All you need to remember is that opposites attract

 

I think I was going to deep on that one. just to make sure thanks.


Thank you Brucee, I like discussion as well, I think it is fun plus it will direct me in the right direction. I am reading a couple of books sometimes it just don't stick in my mind.

thanks though.