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Trendcom 100 (Atari 822) thermal printer葉roubleshooting help needed

thermal printer Trendcom 100 Atari 822

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#1 electronizer OFFLINE  

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Posted Wed Feb 28, 2018 12:56 PM

I acquired a Trendcom 100 thermal printer some time ago—the Atari 822 is a rebadging of this printer. In a previous post, I mentioned the non-standard 20 pin parallel port connector on the Trendcom, and I was finally able to map it out. I have 8 data pins, the strobe, and the busy pin, but the printer doesn't seem to have a fault pin—there are two pins that appear to be unconnected, but it's nearly impossible to see whether there are any traces going to these pins since they are covered by the connector.

 

Using an Arduino, I was able to get the printer running. It's a nice little unit, and capable of bidirectional printing. However, I am getting each character (or most of the characters) printed out twice:

 

Trendcom 100.JPG

 

I found an article in Analog issue 2 where the author mentions the same issue with the Trendcom 100 when connecting it to an 850 interface—most of the characters are printed out twice. Apparently the solution was to add a .01 (microfarad, I'm assuming) ceramic capacitor to the strobe line to fix the timing.

 

I had set up the strobe timing in my Arduino sketch based on the values given in the 850 Technical Manual, so I've at least been able to reproduce the faulty behavior:

 

850 printer port timing.PNG

 

The original strobe pulse length was 37 microseconds and I was waiting 37 microseconds after putting data on the data pins to initiate the strobe. I've played around with these values a bit and can't seem to get the duplicated characters to go away. The last thing I tried was a strobe pulse length of 70 microseconds and a wait time of 500 microseconds between data stable and start of strobe pulse. Any ideas on what I might be doing wrong?

 

It would also be great to find some documentation for this printer (or even better documentation for the 822, since I'm assuming it's mostly similar). I haven't been able to find the line feed character code for the Trendcom, so I have to manually advance the paper.



#2 Nezgar OFFLINE  

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Posted Wed Feb 28, 2018 2:44 PM

There's this at The Internet Archive: https://archive.org/...perators_manual

Looking at the basic example code in the manial, it's not sending anything extra for cr/lf for text lines. I can't remember if the 850 emits both standard ASCII CR+LF or just one.

Edit: woops, 822 has a direct Atari SIO connection, so CR/LF would be handled internally.

Edited by Nezgar, Wed Feb 28, 2018 2:53 PM.


#3 electronizer OFFLINE  

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Posted Fri Mar 2, 2018 9:54 AM

I solved the problem with the duplicate characters—I actually had to shorten the strobe pulse rather than making it longer. According to the Arduino, the pulse is now 7 microseconds, though now I'm wondering how accurate that value is in code.

 

Unfortunately, there's a new problem: I can see the motor running to advance the paper, however, the paper isn't advancing. It looks like the motor is press fit connected to the paper roller bar, and the motor shaft is just turning without turning the paper bar. Has anyone had this issue on an 822? How did you solve it?



#4 _The Doctor__ OFFLINE  

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Posted Fri Mar 2, 2018 10:05 AM

it may be split... you can replace it or search out a new one with set screw...



#5 electronizer OFFLINE  

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Posted Sat Mar 3, 2018 11:12 AM

it may be split... you can replace it or search out a new one with set screw...

 

 

Good call—the plastic coupler between the paper roller and the motor shaft is definitely split. Now the only problem is where I'm going to find a suitable replacement. There's not much clearance where the motor shaft comes through the frame, and the smallest 1/4" to 1/4" setscrew coupler I've been able to find has an outside diameter of 0.42", which may be too big.

 

coupler.jpg



#6 _The Doctor__ OFFLINE  

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Posted Sat Mar 3, 2018 1:23 PM

there is another possibility... spring collet or collet spring.... back in the day I used them for emergency repairs or fixes, many times the business chugged along just fine, the band aid was permanent.

 

an online search of a few of it's off shoots my be useful


Edited by _The Doctor__, Sat Mar 3, 2018 1:23 PM.


#7 electronizer OFFLINE  

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Posted Tue Mar 13, 2018 4:13 PM

I was able to fix the paper roller by using a piece of flexible plastic tubing that was just the right size to connect the roller to the paper advance motor:

 

roller fix.JPG

 

I discovered that the printer has a self test mode, so I enabled it and turned it on. The printer roared to life in full paper advancing glory...only to jam :(

 

On further inspection, I noticed that the heat resistant strip that presses the paper against the print head is covered with some plastic tape that has started to peel off. It's this tape that is catching on the paper and causing it to wrinkle, which is causing the print head to jam. Unfortunately, it looks like the print head was damaged when it jammed and some of the pins aren't working now.

 

platen.JPG

 

So: does anyone know what kind of tape was used to attach the heat resistant strip to the platen? Or, what kind of tape is heat resistant and would work in this application?



#8 Bill Lange OFFLINE  

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Posted Thu Mar 15, 2018 2:13 PM

Do you know the size of the plastic tubing?



#9 electronizer OFFLINE  

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Posted Tue Mar 20, 2018 1:59 AM

Do you know the size of the plastic tubing?


This is what I used:

1/5" ID 3.3Ft 1 Metre PVC Clear Vinyl Tubing Flexible Air Vacuum Water Delivery Pump Hose https://www.amazon.c...f=yo_pop_ma_swf

It’s very hard to put it on straight. If I were going to do it over again, I would remove the paper roller completely, push the tubing onto the paper roller, and leave it for a day or two to stretch a little. Then I would take off the tubing and reinstall the paper roller. It would probably be much easier to get the tubing on with this method since the paper roller is slightly larger in diameter than the motor shaft.




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