Thermal Printer recovery and repair

Making a commercial grade thermal printer work for your shipping and labeling needs.

This entry was started because for some reason throughout all of the years of repairing printers there hasn’t really been a good article about thermal printer repair. Usually when you look-up problems with these types of printers you ether get sucked into trap-sites that are trying to get your contact info. Forums which have a lot of dead links. Or some company that is only out to sell you a new thermal printer instead of fixing or even using the one that you already got. We’re old school Luddites and still believe the internet is a place for information. We will not sell you anything. If you find any of this information useful to you then awesome.

Finding a thermal printer.

In the computer repair and information technology field thermal printers are one of those  devices that you typically see in a shipping/receiving area of a company that prints out all of their labels that they use to tag all of the boxes in their warehouse to keep things nice and organized. Often times during a merger, upgrade, or simply going out of business the thermal printers in companies like this often get thrown right into the trash. Which is one of the most oddest things in the world because if you check Ebay about the going rate of a quality thermal printer they are asking somewhere in the ballpark of hundreds if not thousands of dollars just for one of these units.

The thermal printer that was recovered from being destroyed.

I was really lucky to find this from a company that was going to throw these away as their software was incompatible with this model of printer. It’s a Zebra Z4000 printer which was the predecessor to the Z4M series printer. This thing is pushing almost 12 years old but it still prints amazing. Granted I couldn’t get drivers directly from zebra on this and had to resort to the seagull drivers as zebra wants you to upgrade to the latest and greatest $1000-2000 dollar machine (seagull just wants you to buy their bar-code software at a few hundred). There was even a time where they were selling Z4000’s on ebay for $80 which is a steal even if there may have been some broken parts in the unit.

This unit also came with a 8MB ram card which now-a-days is almost laughable but having a little ram as 8MB is enough to store the far more complicated images that can be thrown at a printer versus the stock 512kb or 1MB of ram that exists in most older zebra printers.

As a bonus it even came with some wax transfer rolls and paper to test with which is nice.

Thermal transfer and direct transfer. What is the difference?

Lets tackle this one at a time.

Thermal transfer printing:

The Zebra Z4000 as shown in this blog is a thermal transfer based printer.

Thermal transfer printing is the older standard of label making on a thermal printer. This method uses an additional wax or resin based roller that operates along the paper path with your media labels. When the print head fires, it releases the wax off of the film and sticks to the label below, giving you your printed out label.The advantage of thermal transfer printing is since your labels are not heat sensitive they will withstand more abuse from things such as sunlight and temperature. The downside of of thermal transfer printing is it is more expensive since you have to pay for a wax roll as well as your labels at the same time. Also, since it does produce a wax film onto a label if the quality of the label is not good then it can be very easily scratched off of the label with a finger nail.

However, in larger printers like the Zebra that is shown in the picture above thermal transfer printing is actually safer on your print head adding an extra layer of plastic between the print head and the labels.

Direct transfer printing:

The LP2844 Zebra Printer is a very common direct transfer printer used in shipping locations around the world.

Direct transfer printing is what a lot of smaller thermal printers do such as your FedEx and UPS self-service Kiosks. Direct thermal is also used in POS environments such as retail as well because the receipt tape can be produced very cheaply resulting in print-out receipts that are 1/100th of a penny per print.

Instead of thermal transfer printing which applies wax to the label direct transfer simply applies heat to a heat-sensitive paper which will force it to change its pigmentation. Since they do not require an extra feed path for the wax roll direct transfer printers can have a much smaller footprint and have less problems go wrong with paper path and loading. Since you’re just buying the direct transfer paper it’s far cheaper. However, the downside of direct transfer is your printed labels will not last as long in the sunlight or in any warm environment (ever have a UPS box that looked very faded after a few years?) . Another downside of direct thermal is if you purchase poor quality labels with a non-existent wax coating it can actually eat away your print head like sand paper. Resulting in your print head life only getting 1/10th the amount of print jobs out of it if you actually paid for good quality labels.

A thermal printer health check.

When you get a thermal printer from a company or surplus auction site. Chances are the printer is going to be heavily beat up. Tens of thousands of pages may have already gone through this printer leaving you wonder if it is any good. The good news is a lot of the damage that a thermal printer sustains is purely cosmetic (stickers all over the thing. yellowing from harsh UV light, missing plastic doors) . However here is some of the advice you may want to check on your next printer which may effect the quality or performance of the model that you are picking up.

Platen or Pressure roller:

One of the easiest things to get destroyed on every thermal printer that you come across is this platen roller. This is what grabs the labels and presses it against the print-head so it makes good contact with the paper. Sometimes during its life someone will tear a label a little too far leaving a part of the sticker exposed so when the printer sucks it back in to print at the very top of the label it doesn’t spit out of the printer instead it rolls around the platen creating a bit of a mess.

When that happens the customer or employee would use a knife to get the label off. Which is an incredibly bad idea! Because the knife will go into the high pressure rubber on the roller and it will begin to split as it rolls against the labels and print head. Your end result is labels that have a ‘flour effect’ where it’s very spotty on how it prints because the platen is so damaged it’s no longer providing even pressure for it to print on.

In my case I was lucky, no major cuts in the platen roller. A little dirty which can be easily cleaned with a plastics cleaner or Windex. Try to avoid alcohol on rollers as it could dry it out and cause it to crack. If you are unlucky and get a platen roller with a few major cuts in it the good news is this is one of the cheaper parts you can buy for your thermal printer. Costing anywhere from $20-$60 US and about a half an hour time to undo your drive belt c-clips to get the platen out (it may be as simple as two plastic tabs on the smaller zebra lines) and it will be as good as new.

The thermal print-head:

The thermal head is the core of your printing process in these printers. It can also be the most expensive. There are some tell-tale signs that you may be encountering print-head issues with a thermal printer if you are able to visually inspect it before you buy (or if the Ebay’er was nice enough to take a picture of the printer in good detail for you) . 

The picture above is a perfect example of how a worn out print-head visually looks. The black resin coating is worn away on the side of this printhead which when its gone it no longer will print in areas where there is a white showing through on this picture. So the best that I could tell is whoever had this printer last did use full-sized labels but the edge of the label was rubbing into the printhead causing it to be eaten away slowly.

Depending if they used third party materials that do not have a good wax coating and also if they were using direct thermal labels versus thermal transfer labels can all factor into the lifespan of a average print head. If you see white dots in the middle of the print head chances are the customer or employee was using different sizes of labels for a long period of time cutting into the printhead at the ends of the label width during direct thermal printing. If the employee was using a thermal transfer method and using a wax roller that spans across the entire print-head then the customer can use whatever size they want without damaging their print head.

A typical zebra print head is capable of printing out hundreds of thousands of labels before totally dying because of the design of resin coating the entire assembly like how they do it.

Also on my printer there was actually different versions of print head that could be bought for this unit. You could get a 203dpi or a 300dpi. After checking the part number in the front of the print head I confirmed it was a 300dpi so I lucked out on getting a higher quality print head.

Print Head defects.

Defects can range from the following:

stripes going down the page. to entire sections of print missing. Replacing print-heads on zebras is relatively easy and requires little to no calibration. However the cost of a printhead new from the manufacturer can range anywhere from $200-$600 dollars depending on dpi of the print head in your Unit.

stripes going down the page can also be caused from excess wax build-up from the customer or employee setting the temperature of label printing way too high resulting in plastic melting onto the printhead. In this case you’re very lucky and all you have to do is with your fingernail scrape the excess plastic off of your printhead. Use windex to clean with a soft-cloth and never-ever use a screwdriver to scrape off excess plastic from the print head!

If your print is solid on one side but almost gone on another and it’s like mine which is a fairly large thermal printer. There is typically tension adjustment screws to position your print head and apply an even pressure down onto the platen roller.

The main drive belts in a thermal printer:

Every printer from the smallest to the largest ether has gear-clusters or belts that drive the platen and move the paper out from its pick-up roll and out of the printer. Because of the immense pressure constantly going on the platen along with daily wear and tear as well as abuse the belts can start to loose teeth and skip. When that happens besides the horrible noises it may make it will also seriously mess up your prints and even cause false errors in the gap sensors on these printer.

This part is relatively cheap. Anywhere from $8 to $50 US to get. And with a little bit of mechanical skill you’ll be able to remove the gears and take the belt out your thermal printer and replace it with a new one. This one was fine and there was no need to replace the belts.

Thermal Printer stepper motor.

Although extremely rare at about a 1 in 100 chance. The stepper motor may also be failing which that part can cost around $15-35 dollars US to replace. That part is also not overly hard to replace on the zebras.

Thermal Printer electronics.

The final thing we’ll talk about very briefly is the electronics portion of the thermal printer since we have the covers off of my zebra printer. In the picture at the bottom is the primary control board. If that board fails your zebra will power on however there will be no status displayed, all of the idiot lights in the front will be solid, and if you’re lucky to have a digital display in the print of your zebra that will be blank as well . In most cases this is due to ether the IT department flashing a new firmware via the ZPL utility that didn’t take. Or they were stupid and flashed the wrong firmware to the printer. Or simply didn’t wait the 5-20 minutes for it to flash , turned off the printer and bricked the unit. In any of those cases the NVRAM chip is gone and unless you had another zebra board to clone from it’s pretty much shot. Aftermarket price for that board is around $150-300 US dollars making the printer not worth repairing and instead parting out for salvage.

You can do some basic tests like remove the upper option card that controls the extra ram. But that’s really about it.

Underneath the control board is the power supply for this printer. Power supplies in the heavier zebras are actually built extremely well. But you can check the fuses if you get a no-power issue.

Media and Wax Sensors of the Thermal Printer:

I should note that not all thermal printers will have a radiant red light like the larger zebra series do.

In direct thermal printers there is only one sensor that senses what is known as ‘marked’ labels where there is an actual black mark on the back of the wax film label. On my printer it senses gap by firing a red light through the media to attempt to find where the break is on the label. If it cannot find the mark or gap on the paper you will often face problems where it spits out way too many labels and will sometimes even error out with a media position error.

With the help my the user manual of my printer I was able to play around with the media sensor until it was sensing paper again.

By holding Pause, Feed, and Cancel all at the same time I was able to produce this test which shows how my media sensors are working. As a note on other printers you may have to do this through pressing or holding a series of buttons to make it print something like this for it. With a little help in moving around the sensors where they should be I got it to finally sense the label (all be it very lightly due to how thick these labels are)

If for some reason you are getting solid black on the bottom no matter what you are doing and despite what media roll you insert there may be an issue with the media detect sensor itself.

Optional Buttons.

Depending on your make and model of thermal printer you may have additional buttons that can be used for adjustment of print quality issues as well as jumper settings on how the interfaces communicate with our PC. With the Z4000 is was behind a trap-door which there is a lot you can do from printing internal tests to restoring the unit back to factory defaults.

Media Defects:

Another way of diagnosing the quality of the printer is simply how it’s behaving during production or printing out a graphical test sample. Since bad parts are thrown away quickly it’s difficult to produce these errors in real-time for you. However, with the aid of photoshop I should be able to replicate what you may encounter out there when picking up one of these old printers.

Good Shipping Label.

Starting the example of labels is how the original label should look coming out of your printer. Where the blacks are solid and crisp and there is no bleeding into the barcodes from the printhead getting too hot. This will be the template label I shall use throughout this guide and it’s pixel ratio is 300dpi at approximately 4inches by 5.8 inches.

Flour/Faded Print.

This happens if the print head is making solid contact on one side of the label but as you look across the label the quality gets progressively worse until it’s almost unreadable or gone. This is caused by the two pressure adjustment guides on the top not applying even pressure down to the platen. If that does not change your print quality inspect your platen roller for any wearing out or cuts as a warped platen roller from abuse or overuse can cause this flouring effect as well. Finally, re-seat the print head on your thermal printer and make sure it is aligned properly.

If you are using a thermal transfer printer and this happened recently when you received a new batch of wax rollers try go purchase one OEM roller as you may have a bad batch of wax rollers that is incompatible with your printer.

Solid vertical no print.

When you have print that exceeds a few pixels on your label this could mean a few things. First, check to make sure that there’s not obstructions of debris stuck to the print-head as any paper or extra wax roller material that insulates the printhead will no longer transfer down to the label. Next, re-seat the print head cable if an entire bank is out like this it could be a loose or bad wire connection in your cable harness on your printer. Finally, if all options fail you then replace the print head.

Small vertical lines in print.

This can happen slowly, or after a large print run. Over time there’s a few pixels on the print head that simply stop firing down to your labels. If only one of them is out not a big deal but if multiple start to fail it begins to impact bar-code scanning. This first thing you want to check is see if there’s any obstructions on the print head. Use your finger to glide across the print head to feel if there’s any build-up. If there is, use either your nail or a plastic pick to scrape the ink and debris off of your print head and try again. Visually check to see if there is any white on your print head as mentioned at the beginning of this article. If there is white spots along your print head then it is worn out and you need a new print head.

Print cutting off and loud noises.

This is a symptom of either the gear cluster giving away or the belts slipping, resulting in print shuddering  and possible error due to loosing label positioning. If possible, remove the coverings and inspect the gears and belts of your thermal printer. In many cases, the damage is very obvious especially if you have the capability of running the printer with the coverings removed from it. You will probably need a new belt of gear cluster assembly depending on make/size of your thermal printer.

Print too light!

Light printing can effect the quality of your darker areas giving a flour-like effect but still retaining its clarity unlike the previous error. But light printing can also effect the readability of your text and can effect bar-code scanners. In most cases you can control this in the driver for your thermal printer. As an example, zebras can go from 0 to 15 in print heat. Ideally you would like to be somewhere in the middle where the blacks are solid but not bleeding and the pixels around the text is solid and crisp. Check the speed of your thermal printer and see if you can slow down the printing so the printhead has time to apply heat to the label. If you are already at the maximum density and you are still getting light print then you may be looking at a defective print head.

Print too heavy!

The opposite effect is if your head is too hot it will transfer too much ink down to your labels, you will loose detail in your labels and it will be increasingly harder to scan your labels as a result. Also, because your print head is so hot your life expectancy is reduced as a result. This can happen if this printer used to operate at a very high speed but does not anymore due to a software change. Once again, you can ether set the darkness on the printer itself if your driver is running all default or you can adjust the darkness settings inside some of the thermal printer drivers

Repetitive Horizontal Lines.

This is a problem dealing with a possible driver incompatibility issue and may have nothing to do with your thermal printer. To verify this perform the internal tests as stated in your user manual and if you do not get those lines without it plugged into a computer and printing from its own internal memory then it’s more of a software issue then hardware.

Check out the following blog.

Printing labels with your thermal printer.

End thoughts.

We hope this information will serve you well. And perhaps save a few thermal printers from hitting that dumpster just because it longer conforms to the rest of the company. Thank you for reading.

Leave a Comment