Trendcom 100 (Atari 822) thermal printer—troubleshooting help needed

[electronizer]

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:

 

 

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:

 

 

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.

[+Nezgar]

There's this at The Internet Archive: https://archive.org/details/atari_822_operators_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 February 28, 2018 by Nezgar

[electronizer]

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?

[_The Doctor__]

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

[electronizer]

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.

 

[_The Doctor__]

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 March 3, 2018 by _The Doctor__

[electronizer]

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:

 

 

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.

 

 

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?

[Bill Lange]

Do you know the size of the plastic tubing?

[electronizer]

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.com/dp/B00KRB3L30?ref=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.

[jnharmon]

On 3/13/2018 at 6:13 PM, electronizer said:

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:

 

 

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.

 

 

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?

If you are still having the damaged print head problem, I have a package of replacement print heads for the 822 and could send you one.

[electronizer]

Thanks for the offer! I did a close inspection of the print head and discovered it was just dirty. I was eventually able to get it working again.

 

I can also update on the platen tape—I talked to Brad at Best Electronics and he thought it was probably teflon tape. He sent me a piece and it worked very well to replace the old peeling tape. The printer now works fine!

 

Now if I could only find the Macrotronics interface that works with this printer (uses joystick ports 3 and 4, mentioned briefly in Analog #2, page 42). Since my original post I also acquired a Trendcom 200 (80 column thermal printer). Macrotronics published some screen printer software that works with the 200 and it would be fun to try doing some screen dumps. From what I read, these would have been some of the earliest printers available to Atari users.

[joeventura]

Is the trendcom Mechanism swap-able with the 822?

[gilsaluki]

Looking for one.

[+joeatari]

Does anyone know the size of the O ring in the photo?  Is there supposed to be more than one on the roller or just that one?  Thanks!

[+joeatari]

I tried a #6 1/4 X 7/15 X 3/32 (BG) O ring. (This is the part number from true value hardware: 02-1450P), and it is advancing the paper now.  It is still "rocking back and forth" a bit so the lines are crooked unless I pull on the paper to keep it taught.  It doesn't seem to be missing anything else, but I supposed something else could be missing.  I tried two O rings, one on each side, but it only seems to work if it is on the very left side (when facing the front of the printer).  I didn't want to take it apart again, so I just moved both O rings over to the left, and it did seem to give it a little more traction.  I discovered that it advances the paper much easier if the screws on the stepper motor are a bit loose so the motor can move around a bit.  Yes, that is super glue on the part that connects the roller to the stepper motor.  I'll probably try the tubing solution, but it is holding just fine for now.

 

[_The Doctor__]

Your o rings are a fraction too small in outer diameter,

putting two on the left and two on the right might help.

the servo motor might be pulling too tight again the o ring closest to it.

you can loosen all servo screws and riser mount screws then re tighten them with the tension towards the back it will level the pinch/paper control rod and make the pressure more even across the length of the rod