IBM 5140 PC Convertible Printer

[Cyberstein]

I recently purchased 2 IBM PC Convertible printers. One came with an IBM 5140 PC Convertible I purchased and the other was NOS from TexElec. I knew the one I bought with the PC was damaged as they stated so in the listing. It's paper release was broke, which I was able to repair. When I tested though, It skips every other line I print. I then tested the NOS one from TexElec. It was worse, it would not move it's print head. I opened it up and found mechanical damage in two places, which I was also able to repair. I then tested it and to my surprise, it also is skipping every other line. That being said, I have two printers doing exactly the same thing. Other than skipping every other line, they both work perfectly otherwise. Has anybody else ran into this issue? It must be common if I have two of them doing the same thing. It does this when I print screen, print from DOS Edit, and even from the print diagnostics. If anybody has any insight into this, let me know. I did find someone stating this issue on Reddit, but I am not convinced of their finding/solution. If I find the issue, I'll post it. Thanks!

 

[modem7]

1. Do you have two cables, or are you moving one between the two printers ?
2. Powering on the printer before the 5140 ?

 

[Cyberstein]

My configuration is as follows:

5140 PC -> Serial/Parallel Adapter -> CRT Adapter -> Printer Cable -> Printer

In regards to powering the printer before the PC, it is powered by the PC at the same time. I have also tried connecting the printer directly to the PC with the same results. That is in this configuration without the Serial/Parallel Adapter and CRT Adapter and printer cable:

5140 PC -> Printer

 

[Cyberstein]

Here are my observations thus far. I think the following is the correct behavior.

1) Print head should be held forward against paper, printing ,and printer cartridge moving when moving right.
2) As the print head reaches the far right, the paper should advance one line. This paper advance plays a role in the head control gears as well.
3) Print head should be held back away from paper, not printing and printer cartridge not moving when returning left.

What is happening in my case.

When the print head returns nears the end of the left return at the far right. It momentarily goes to the correct position against the paper indicated in step 1 above. But then immediately pulls back away from the paper. Where it should be printing at this point but instead is being held away from the paper. Which is why it is skipping every other line. This appears to be a mechanical issue, such as a catch not catching when it should. I will observe further and see if I can't find the issue. Given this is happening to one user on Reddit and on two of my units. It should be a fairly common failure I would think.

 

[mbbrutman]

I've had this happen twice; once with a new-old-stock printer on eBay and once on a printer I've owned for years.

There is a design flaw in the printer mechanism. One of the springs or the plastic it is attached to eventually warps under pressure and causes the printer to not print every other line.

Here is a quick video of my terrible fix - a bent paper clip with just the right amount of bending on it to give the mechanism the proper amount of tension:

Link to Google photos: https://photos.app.goo.gl/DBucuLADJ75zLS4q7

 

[Cyberstein]

Yes, I actually fix the same issue. I also fixed in a similar way. I have video, if I can get this darn thing fixed I’ll post it. Perhaps I need to increase the tension. Thank you for the info! When I get some more time, I’ll increase the tension on it and see if that fixes it.

 

[Cyberstein]

I soldered a wire to the original spring and clipped it to nearby clip.