Won't print large font in solid black. Only prints outline of letters in black

What size tape are you using? If you have switched from half-inch to quarter-inch tape, then chances are that the printer is working correctly as the general size of the print is determined by the size of the tape. Beyond that, you can use the Text button at the top-center of the keyboard to enter the options for customizing the print such as the font used, the size (small, medium, or large), the width of the letters, and the style (such as bold, outlined, or shaded).

You have to change print size by choosing a larger font in the software you used to produce the document.

Assuming you're referring to the print size of the fonts - letters ..... or the size of the printed page ...
If you're printing from your computer, you'll need to change the size of the font (to a larger font size) on your document before you print, or adjust the print Properties ... to fit to page, or magnify the size of a small document ...
If you're printing a pdf file, you can specify the size of the document using the enlarge (%) before you send it to the printer

Problem is with carriage unit.

I suspect this is happening because your "Font" is set to Red. What you need to do, is when in the document, go to the Tool Bar and find & select the "Font" and change the color to Black. It is usually a little "Box" at the side of the name & size of the Font, you click in here and another little popup will appear showing colors, simply click on the Black color, and it is done, set.

More than likely this a "Fontcall" error from within the application.

What normally happens is that you design a document in Word and select a font that is resident on the PC but has not been downloaded to the printer.

When the document goes to the driver, the driver sees the call for a font that it does not have in its index table and then does a :Best Fit" algorithm.

The output is usually very unexpected.

As a quick test, do a "<ctrl>+a" to select the entire document. Then change the font to Arial. Now see if the font on the screen matches the font on the printout.

If it does, either make sure you can get a "Soft Font" rendering of the font you want. Soft fonts will download automatically to the printer.

Or you can check with a company such as Font Mongerer to see if they have a printer font that matches the screen font. Once you purchase the font and download it to the printer you should be fine.

Don

If you can print the nozzle test then that proves most of the electronics, it could be the driver is screwed.
Since you can get something out that is intelligent e.g. the larger font lettering then it is processing the file sent to it.
By that I mean rasterising it, converting it to dots of ink, so it can print onto the page as the heads moves back and forth.
Why not try another computer and connect your printer to that one, or try a different file, or even send it a file you've printed successfully in the past before you started to have this problem.

Usually, the size of the letters depend on how large you have them in your document. Open your document, highlight the letters you wish to change (or the entire document if you want to change everything) and from the menu bar at the top of the screen, (Usually under "Format") you will find a "Font" selection. Increase the size of the font by selecting a larger number. This will change it on your screen as well as when the printer prints it. You may have to save the changes before printing.

does this happen though the document feeder or on the main glass if printing was fine then black cartridge and drum are ok its the scanner roller replaced or there something causing a problem

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

Trouble with the HP Laserjet printed output may be solved by using the following settings (or similarly named ones): "Use raster Graphics" (instead of "Use vector graphics"). This may fix the problem of "reversed" text (white on black background) not printing, as well as other problems. "Download TrueType Fonts as bitmap soft fonts" (select "bitmap" instead of "outline" or "graphics"). This may remove the overlapping of text on the printed document. "Graphics dithering" select "coarse" or "fine" (instead of "none"). This selection may improve the quality of images contained in the document. You can find all these settings in your printer properties. Go to File, Print, click Preferences, in Printing Preferences, click one by one all the top options, and change one of the top solutions, one at the time, checking your printing output. Always check if you have the latest version of Adobe Reader Program. If not download the latest version from Adobe, it's free. Is this the first time that you have the problem? or with the same printer (HP 4si), did you were able to print PDF files in the past?