NewDeal Hot Tip 1807

[Hot Tips for...] Printing

White Lines or Squashed Characters

If your dot matrix printout has white lines or "squashed" characters, try printing using the friction feed option on your printer, instead of the tractor feed.

If the friction feed does fine, then the problem is isolated to the gear train that is feeding the paper into the printer in continuous feed (tractor feed). This means there is enough wear in the gear train to allow the paper to shift a little bit (maybe just 1/64 of an inch). This translates into the printed line being out of position by that much.

When you use Text Only mode, or when you print from another one of your DOS applications that prints in text mode, the internal fonts of the printer are used to print the characters. When the internal font is used, the characters on each line are made in one pass of the print head. This means the characters are always the same height on every line and the paper is not moved except between lines of characters, so the problem may not be apparent. If you still get white lines when printing in Text Only mode, then it's likely that one or more of the pins in your printhead is stuck, missing, or not working.

When you use High or Medium mode (not Text Only), or when you use another DOS application that prints in graphics mode (a drawing program, for example), the internal fonts of the printer are no longer used. When you want to print a character, the software has to "draw" the character on the paper, emulating the height of the character by a certain number of dots (as in Dots Per Inch or DPI). For example, let's say the character is 12 points high. That's about 5/32 of an inch. Most nine pin printers print graphics 8 pins at a time and make multiple passes over the same area to lay down even more dots. To make this character on a 9-pin printer in medium mode of 150 DPI may take 4 passes and result in a character 23 dots high.

Now the problem: The paper is micro fed by the program telling the gear train to move as little as 1/64" each time. If it slips a little on the tractor, or the paper bail is away from the friction roller, or if the gear train binds a little and doesn't move the required amount or moves a little too much, then the next pass of dots laid on the paper will be out of place and will distort the printout resulting in smaller characters or white lines.

An 'italics' look could be caused by the paper slipping left-to-right. Make sure the paper bail is down and check for excess movement of the paper left-to-right. It can also be caused by the printer printing bi-directional (both ways) and the right-to-left pass of the print head is out of alignment with the left-to-right one.

If the characters are smaller or squashed looking, this is an indication the gear train is not moving the full amount required.

Be sure the paper is not binding or rubbing against anything on its way into the printer. If that's not the case and the problem persists, you may need to clean the gear train and apply a little light machine oil or grease. It is best to have the machine serviced by a dealer: they know what to look for and have the specs on the oil, grease, or whatever is needed for the job.

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Last Modified 6 Mar 1999