HP LaserJet IIIP+
paper jam if more than a dozen pages in the paper tray

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The lines would be a toner cartridge problem. Which paper tray? The MF tray or the optional paper cassette?

How to Identify and Fix Common printer Problems ?

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The printer`s default print margins are 3.0 mm (0.118 inch) for the top, right, and left margins, and 12.7 mm (0.50 inch) for the bottom.
Conclusion. If your laser printer is causing horizontal black lines you either have a problem with the optics or the drum. Cleaning the optics and replacing the drum should fix the problem in most cases.
A printer printing lines on the page are normally caused by a blocked, dirty, or damaged print head. Blocked ink cartridge nozzles, or not removing protective seals correctly when you installed a new ink cartridge can also cause missing lines of print.
Continuous paper:

The minimum left and right margins are 13 mm (0.51 inch) each. The maximum paper width is 254 mm (10.0 inches). The maximum printable width is 203.2 mm (8.0 inches).

Streaks and unwanted lines could mean that the printer heads are out of alignment. There`s an alignment tool in the printer`s control panel. If that`s not the issue then the printer is dirty. Printer ink stripes may appear along the edges of the paper, which means there`s ink on the rollers and other parts.
There are four primary causes for horizontal banding on prints from inkjet printers, (1) nozzle clogs, (2) mis-aligned print heads, (3) low quality print settings (4) incorrect paper thickness settings. Below we will describe each of these causes for horizontal banding as well as ways to try and fix them.
If the printer is in Line Print, it will print any content as required. However, it will not interpret the commands unless you set the printer to ZPL or EPL mode. For example, if the printer is in line-print, send this command: ! U1 setvar “device.languages” “line_print” The command above will print on the label.
The streaks or lines might be caused due to low ink levels in one or both ink cartridges. Check the ink levels using the HP Toolbox to determine if the ink cartridges are low on ink and need to be replaced. note: Ink level warnings and indicators provide estimates for planning purposes only.
The band-shaped “stripes” are called “horizontal bands” or “banding.” Horizontal bands are caused by the subtle changes in the movement distance that occur when feeding the media depending on the media`s thickness. We recommend making corrections to match the media you are using.
Every printer is different, but general safe margins for each size are: 8.5 x 11: 0.25in on the top, left, and right, and possibly more on the bottom, like 0.5in. A4: 5mm on all sides, or 10mm to be extra safe.
Most desktop printers can`t print all the way to the edge, thus leaving you with a non-printable margin. While the exact dimensions vary from printer to printer, the limit for most models is 1/4″ (0.25″).
Look in the technical specifications section for information on the top/bottom and left/right margins. Another easy way to find the margins is to use Microsoft Word. Change your default printer to be the printer for which you want to identify the margins. Click the Margins button and then click the Custom Margins…
Both the MLA and APA style guides require 1-inch margins on the top, bottom and both sides of the page. In most cases, when you open Microsoft Word, the margins will already be set to 1-inch.
Click: `Open the HP Photosmart Toolbox` or: `Service this device` Click: Device Services tab. Click: Calibrate the Device or Clean the Print Cartridges or Align the printer. Follow the instruction which will appear on-screen.
Faint, streaky or spotty prints are all common signs of a clog but a simple cleaning can usually get your HP ink cartridges working again. Printheads clog due to infrequent cartridge use. If you regularly go a few weeks without printing, your cartridges will eventually dry out and need to be replaced.
Most desktop printers can`t print all the way to the edge, thus leaving you with a non-printable margin. While the exact dimensions vary from printer to printer, the limit for most models is 1/4″ (0.25″).
On the Page Layout tab, in the Page Setup group, click Margins. Do one of the following: To use predefined margins, click Normal, Wide, or Narrow.
Look in the technical specifications section for information on the top/bottom and left/right margins. Another easy way to find the margins is to use Microsoft Word. Change your default printer to be the printer for which you want to identify the margins. Click the Margins button and then click the Custom Margins…

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

evenly spaced horizontal lines on hp laserjet III printout
ANSWER : The lines would be a toner cartridge problem. Which paper tray? The MF tray or the optional paper cassette?

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HP LaserJet IIIP+

Hp laserjet 2420dn
ANSWER : I would suspect the fixing film has wear. You can prove the theory by doing a half-stop test. This stops the print before it enters the fixing film assembly. Load paper in the drop down MF tray in the front. Send a print job and when the tail end starts to enter, open the cartridge lid on top to stop it. Then remove the toner cartridge and look at the paper. If you see the marks, it is from the toner cartridge. If you don’t, it would be coming from the fixing film since the paper hasn’t entered it.

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HP LaserJet IIIP+

HP Laserjet 4250 – RFU LOAD ERROR
ANSWER : Italiano:

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HP LaserJet IIIP+

HP Laserjet M3035xs RFU Upgrade
ANSWER : There’s no way.

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HP LaserJet IIIP+

HP Laserjet 4200 50.2 Fuser error
ANSWER : if you are using a good fuser the next part to try would be low voltage power supply

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HP LaserJet IIIP+

How to copy a card slot in HP laserjet 4250N
ANSWER : None that I know of, using a computer is likely your best option but I never attempted it.

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HP LaserJet IIIP+

HP laser jet 3015 "Upgrade Error Call HP Support"
ANSWER : rgtr

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HP LaserJet IIIP+

HP LaserJet 2200D won't print configuration page
ANSWER : Find someone with a HP LaserJet 4100 and you can configure the card to the IP you want:

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HP LaserJet IIIP+