Troubleshoting Printer HP

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For a comprehensive discussion of strategies for troubleshooting printing problems, see Appendix D, "Troubleshooting Printing Problems."

General Printer Troubleshooting

  • Make sure the printer has power and is on-line. If you are using a manual printer sharing device, make sure the switch is set to activate the correct printer.

  • Turn it off and on again to reinitialize any internal settings that may have gone astray.

  • Use the printer's own self-test, according to the manufacturer's recommendation. If it fails, you have verified that the problem is within the printer. If the print head is not moving at all, the transport motor may have failed.

  • If the printer passes the self-test, try a test print using the Print Screen capability within DOS. If the Print Screen fails, you know the problem is in the relationship between the printer and the computer. Inspect the cable and the cable connections. Replacing the cable with a known good cable is worth trying since cables are so frequently the source of printer problems. Cables can fail with broken wires, loose or broken pins, or incorrect pin-outs.

  • The message "out of paper" is sometimes erroneously reported when there is plenty of paper, and can indicate a physical problem with the printer.

  • If the Print Screen succeeds, the problem may be with your application or its configuration. For example, your application may be set up to direct output to a file instead of the printer, or you might be directing the output to the wrong communications port.

    WARNING! Some printers differ from computers in that they do not have shielded power supplies. That means that a plugged-in printer can expose you to full outlet power, which is enough to kill you. Never open a printer case unless it is unplugged!

Troubleshooting Laser Printers

  • Be sure all dip switches are properly set for your configuration. Laser configuration is sometimes done by a control panel of buttons with an LED display that permits you to alter configuration memory. Be sure that the application being used is properly configured for the printer as set up.

  • Fuzzy laser output could mean you have a dirty corona wire or you are running out of toner. Horizontal lines or splotches indicate possible damaged or dirty print drums or rollers. Since some of these components are part of the cartridge, a useful quick fix is simply to change the cartridge.

  • If laser images seem disproportionately long or short, the drive motor may not be moving the paper through at the correct speed.

  • Failure of a laser printer to go on-line might be a communication interface problem. It could also indicate a faulty control panel. Try powering up the printer with the cable removed. If it now goes to "ONLINE" (or "READY"), suspect the cable or its connector.

  • If you are printing totally black pages, suspect a broken or fouled corona wire. If that is not the case, replace the toner cartridge.

  • If the print appears speckled, it is probably the fault of the primary corona grid which is part of the toner cartridge. Replace the toner cartridge.

  • If white streaks appear in your printing, shake the toner cartridge to insure an equal distribution of powder. If that doesn't work, clean the transfer corona assembly. Contamination on the assembly will prevent it from holding the electrical charge needed to attract toner from the drum.

  • A repetitive pattern of printing defects, such as an identical smudge every 2 inches may indicate a defective fusing roller. Try cleaning it according to your hardware vendor's instructions. If that does not work, you may need to replace the fusing roller assembly.

Troubleshooting Dot Matrix Printers

  • If the printer self-tests OK but will not print jobs from the computer, check the following:

    • Dip switch settings

    • Proper driver for your application software

    • Bad or disconnected cable

  • Some printers have both serial and parallel connections. If one doesn't work, change cables and try the other. Be sure to change any dip switch settings needed by the printer to acknowledge the change. If this works, you may have had a physical problem with the output port on the computer or the input port of the printer that you tried the first time.

  • If a dot matrix printer shuts down and recovers frequently, it may be having problems with its "thermistor". A thermistor is a device used to keep the printer from overheating. Try replacing this part before you replace the entire print head.

  • Some printers can be set by dip switches for unidirectional or bidirectional printing. Bidirectional is normally faster, but might cause problems with graphic output for some combinations of applications and printers. If you suspect this problem, reset your dip switches for unidirectional printing.

  • If your output is double-spaced when you expect single-spaced, you may be getting an extra Carriage Return and Line Feed at the end of every line.Reset the dip switch(es) controlling this.

  • If your print quality is poor, first check the ribbon for wear. Also examine the print head spacing. Your head may be too far away from the platen for your current paper thickness. If adjusting the spacing doesn't solve the problem, clean the print head itself with a cotton swab dipped lightly in alcohol.

Troubleshooting Network-Related Printer Problems

The following information may be helpful in resolving printer problems. For a comprehensive discussion of printing troubleshooting, see Appendix D, "Troubleshooting Printing Problems."

  • If a network printer sometimes goes off-line for no apparent reason and works fine when it is reinitialized, you may have a static problem. Large amounts of static can be generated by certain special papers, such as carbonless forms. Make sure your printer is properly grounded.

  • Plotters need to function much as printers in order to accept a job to plot, but plotters can have no direct interaction between themselves and the application.

    For example, the AutoCAD application talks directly to a COM port, then waits for a reply from that port. Since NetWare® software only redirects printing to LPT ports, AutoCAD ends up waiting for COM port activity when there won't be any.

    You can handle this problem by saving a print job to a file and then using NPRINT or PCONSOLE to print the job. An alternative would be to plot to a file named "LPT1" after capturing the device LPT1 with the CAPTURE command.

Serial Communications Channel

Serial (RS-232) communication channels usually depend on certain control codes, such as X-On/X-Off, being sent as part of the data stream. A PostScript job on an RS-232 channel may include additional control characters to perform these tasks:

  • Request printer status (0x14)

  • Interrupt the PostScript interpreter (0x3)

  • Signal the end of a job (0x4)

Other control codes may also appear, such as 0x1, 0x11, 0x13, and 0x16, which perform similar functions.

When a serial printer receives a data stream containing control codes, the printer's communications interface traps and removes the control codes. When this is the case, it means that the serial channel is not binary-capable.

If you direct binary data to this type of communication interface, some data values will be misinterpreted as control characters and erroneously stripped out. This, obviously, will affect the printer output, and cause distorted or garbled printing.

Also, a serial channel may be configured to use less than 8 bits of data per character, as described in the next section.

Parallel or Hewlett-Packard Remote Printer Communications Channel

Centronics Parallel and Hewlett-Packard Remote Printer communications channels use 0x4 (Control-D) to signal the end of a job to the PostScript interpreter, or 0x3 (Control-C) to interrupt the interpreter, primarily because of the precedent set by the serial channel. This means that parallel and Remote Printer connections are also not binary capable.

DOS PostScript Applications Generating Control-D

Many DOS and Windows applications generate PostScript to be sent to a printer across a serial or parallel interface. These applications include the Control-D (0x4) character to signal the end of the job. If this data is sent to a queue serviced by an AppleTalk printer, the Control-D character will be passed to the printer's PostScript interpreter instead of being intercepted by the printer's serial or parallel interface. This can cause PostScript errors or job failures from these applications. ATPS solves this problem by filtering jobs for Control-D characters and replacing them with Printer Access Protocol (PAP) EOFs.

NOTE: Other DOS and Windows applications may generate binary PostScript data, which could use Control-D as data rather than to signal the end of a job. For these applications, you should create a print job configuration using the "PostScript (Binary Graphics)" mode in PRINTCON.

Preventing Printer Problems

Appendix B Cabling Printers

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