HP LaserJet 4

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Great instructions. Also check this out on how to disassemble the printer:

How to Identify and Fix Common Problems ?

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Turn off the scanner and unplug the AC adapter. Wipe off any dust or dirt on the glass scanning surfaces using a soft, dry cloth. If the glass surface is stained with grease or some other hard-to-remove material, use a small amount of glass cleaner on a soft cloth to remove it. Wipe off all remaining liquid.
Never use alcohol, thinner, or corrosive solvent to clean the scanner. These chemicals can damage the scanner components as well as the case.
Clean scanning means the illegal act of an air care station or air care inspector that results in a fraudulent “pass” for a vehicle`s emissions test by entering into the emissions analyzer unique information identifying the vehicle being tested, but then performing the emissions test on a different vehicle, which …
For cleaning, HP recommends using HP Equipment Cleaning Wipes, but you can use an HP-approved lint-free wipe and deionized or distilled water. Note: If dark spots appear on back side of prints, clean drum screen. Note: If minilab prints more than 2000 prints each day, clean drum screen up to twice daily.
Spray disinfectant solution onto a lint-free cloth or paper towel if you`re making your own wipe – don`t oversaturate. Using a circular motion, thoroughly wipe the handheld grip and trigger of the scan gun for 20-30 seconds. Clean the rest of the device housing for an additional 20-30 seconds.
Use only glass cleaner to clean the scanning strips. Avoid cleaners that contain abrasives, acetone, benzene, and carbon tetrachloride, all of which can damage the scanning strips. Avoid isopropyl alcohol because it can leave streaks on the scanning strips.
Lightly dampen a clean, lint-free cloth with bottled or distilled water, and then squeeze any excess liquid from the cloth. Press the cloth against the rollers and rotate them upwards with your fingers.
Locate your printer`s internal pickup roller. The roller is gray or black, and it is made of rubber. Lift the roller upward, towards the front of your printer. Pull the roller gently out of the printer and lay it on a clean surface, such as a desk or workbench.
Locate your printer`s internal pickup roller. The roller is gray or black, and it is made of rubber. Lift the roller upward, towards the front of your printer. Pull the roller gently out of the printer and lay it on a clean surface, such as a desk or workbench.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

HP3330 – How to Clean Scanner Mirrors
ANSWER : Great instructions. Also check this out on how to disassemble the printer:

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HP LaserJet 4

How to I clean the optics inside my scanner
ANSWER : There’s a small glass on the left side of the big one. There’s one Torx screw holding it. Remove the glass and you have access to the optical mirrors. You can either blow it out with an air can or use a cotton swab and clean the mirrors with that. If the mirror assembly isn’t parked under the glass, then start a copy with the ADF and when the mirror parks, pull out the plug.

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HP LaserJet 4

scanner failure
ANSWER : That is a pretty old machine. You won’t be able to get any parts for it. Time to get a new one.

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HP LaserJet 4

All panel lights blinking, printer doesnt respond
ANSWER : This is very easy process, you must change a new one

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HP LaserJet 4

Clean Printing
ANSWER : Simply look at the drum and the belt. If there is still a latent image on either one, that is what you should replace.

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HP LaserJet 4

Product not working suddenly
ANSWER : Since there aren’t any parts available and this looks pretty much fatal, it would be time to buy a new printer.

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HP LaserJet 4

no color cart. new & clean
ANSWER : yes

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HP LaserJet 4

cleaning nozzles
ANSWER : Inject cleaning solution down into the heads. You can search Epson head cleaning kit on Ebay

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HP LaserJet 4