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I have an 82143A printer that prints the right most character lighter than the rest of the print line. In the middle intensity setting, it's barely readable, while the rest of the line is fine. If I set the intensity to the highest setting, it's readable, but the rest of the line is a little darker than it needs to be. I'm assuming there is some sort of alignment problem and I'm wondering if there's a way to correct it. Thoughts?
Steve
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About the only thing it could be is the spring loaded platen that sits behind the print head. It is a strip of metal with a rubber liner. It has a notch along its length that sits over a ridge on the printer mechanism. Sometimes it becomes knocked out of alignment. A related item is the teflon impregnated strip of fiberglass that is draped over the platen. Make sure it is not folded, etc.
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Is it possible to get at the platen easily? How do you remove the plastic backing? Thanks,
Steve
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The platen is easily visible from the front of the printer. It just sits behind the printhead where it is held in place by sping tension. You should be able to see if it is in place and adjust it with your fingers. Press along the path that the printhead travels and you should feel the spring loaded platen bar.
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Hi;
I completely agree with David's analisys, because I had another possibility in mind and did not think about it. At least so far. Thank you, David; yours is a very reasonable solution.
What I remember is that I had a roll of thermal paper and I noticed that at the leftmost characters were dimmer than the rest of the "printing". But this was just in the first 1/5 of the roll. It seems the thermal chemicals in the paper surface reacted with atmosphere or with any other agent (sunlight, temperature, etc.). This is also noticeable when using stocked thermal paper for the first tiem: the first two-three turns of paper are lighter than the rest of the roll.
Just try with another roll before proceding with the disassembling. If necessary you should do it, but checking first for this possibility may save time and labor.
Hope this helps.
Luiz C. Vieira - Brazil
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I tried an experiment, I cut the right edge (1/2" or so) off the paper. After several attempts of the paper getting jammed, I finally got it to print on the narrow paper. The result was the same, with the right most character being lighter than the rest of the line. This was a good suggestion however, since the paper I'm using is old and it's storage over the last 20 years is not known to me. So, thanks Luiz.
I then attempted to gently move the right side of the platen closer to the print head (while the head was on the left side). Since it is spring loaded, it pretty much returns to it's original position, and the result was the same, the right most character was lighter.
I'm going to experiment more tonight, but I don't really see a way to adjust the platen permanently. Thoughts?
Steve
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Hi, Steve;
I'm sad you did not get success so far. Unfortunately I see no other way than disassembling the printing mechanism and removing the platen so you can work with fair "space".
Maybe I am wrong in this following analisys, so I ask for others knowledge and correction, plese. Topcats (HP91, 92 and 97) and the HPIL printer HP82162A use a printing mechanism that is close to the one in the HP82143A with a few differences. If they all have the same platen to adjust paper pressure, it's not going to be hard to find a replacement. In this very forum, some months ago, at least two of the contributors mentioned having printers with problems: one HP82143A and another one having a topcat, don't remember which. If you find an HP82143A with electronic problems, you may replace the entire printing assy and then you will have enough time to repair the other unit and keep it as a spare. If there is one with problems in the printing head (and that's what I read about here) then you'll have to replace the head with yours.
Not so much of help, but it is another possiblity.
Hope you have success.
Luiz C. Vieira - Brazil
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Seems to me that a misaligned platen would produce a continuous fading - that it is : each character closer to the right edge would get lighter. Even the rightmost character would have a leftmost column darker that the righmost column.
If that is not happening, my guess would be dirt on the pins that carry the printhead, causing the printhead to move away from the platen at the rightmost position.
I´ve completely dismantled a topcat printer, and managed to get it togheter ok. This was my first experience on this, and having a exploded parts drawing helped a lot. I got this drawing on the HP Journal article about the HP-91, from a PPC cd set. I don´t think I have a drawing for the 82143, sorry.
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The basic mechanics of the 82143A printer and the HP9x printer are the same, but they are quite different in several respects. The 82143A is belt driven and uses a different print head. Also the head sensor is different. Both printers are built on the same mechanical frame though.
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