HP Designjet color calibration issues

The problem

This is hopefully a highly technical discussion about the HP Designjet (specifically the Z2100 – though this may include others like the Z3100 and Z3200).

I am the owner of PRGPrinting – a fine-art photography printing business. We are located in Westland Michigan. We offer photo printing services for all photographers – beginner and professional.

If you have owned and operated any of the Hewlett Packard Designjet Photo printers (collectively “Designjet” for this article), you will eventually run into the following issue: “Calibration cancelled due to a scanning issue”. This issue primarily occurs during the creation of a new paper profile for the printer. If you Google for that phrase, you will come across several articles describing the problem. Unfortunately, no real solution is revealed.

People have tried changing settings, erasing settings, changing various parts, cleaning parts and so on to fix this problem – with no real solution at hand.

Symptoms

In my case, I have several papers that just simply will not properly calibrate within the printer. Papers like Epson Enhanced Matte and Breathing Color Signa Smooth produce this error. The symptom is always the same – the printer goes through the entire calibration process:

  • print the scanning pattern
  • let the ink dry
  • scan in the entire pattern
  • eject/cut the paper
  • report on the screen that the calibration is cancelled due to a scanning problem

and the creation of the paper profile fails.

The bigger problem is there is no indicator, no log or error display other than the vague “scanning problem” message. The maddening part of all this: some papers calibrate just fine on the same printer!

Things I have tried to get past this:

  • cleaning the printheads from the control panel
  • manually removing the heads and cleaning both the ink egress point
  • manually cleaning the printhead electrical contacts
  • cleaning the “eye” part of the color spectrophotometer (the ESP device)
  • examining and cleaning the line sensor
  • removing built-up ink on the encoder strip
  • replacing printheads
  • executing the head alignment procedure
  • invoking the paper advance calibration
  • running the gamut of service calibrations within the power-on service menu.

Diving Deeper

After getting very frustrated with this problem, I decided to have a deeper go at it and see if I could get into the “firmware” of the machine. The formatter board on these printers is essentially a 80386 based computer. What’s more, the firmware is nothing more than an old version of Linux customized by HP for the printer. Internally, the Linux is referred to as “Troya Linux” and the version in my printer is “2.0.8”. The Linux Kernel on this install is 2.6.10 – a fairly old version of Linux but usable none the less.

I was able to log into the Linux instance on the printer by ssh’ing to the management address and logging in as ‘root’ with no password.

Screenshot of the Linux instance on my Designjet printer
Logging into the Linux that runs my Designjet Z2100

While there are some interesting little tidbits that can be found once logged in, the important thing is to find log files – any relevant log files – to help me figure out exactly what is failing (obviously – so it can be fixed).

Where I am at now

That is where I am at right now – trying to figure out exactly which log file to examine that indicates the paper calibration status. There are log files scattered about the entire filesystem on here: /tmp, /var/log, /vobs (which is apparently where most of the printer specific software resides), and so on. Apparently, there are several log files at least on mine that date back to when the printer was apparently commissioned (2008 – I haven’t owned this printer THAT long).

I expect that this will be a living document to chronicle my journey in figuring out this problem with my Designjet. Hopefully others will find useful things in here as well.

Computer Passwords

Strong Computer Passwords

Computer passwords and security.  Why all the fuss?  Why can’t you just pick something simple and use it everywhere.  Why does your work make you change your password every so often?  Why do they make me use letters, numbers and symbols in my passwords?

Computer passwords are the keys to the digital kingdom of you.  Passwords are how you let some service, whether is it a server at work or something on the Internet like Facebook, know that you are who you say you are.  This is important: just because I say that I am “Mike Smith” does not mean that I am really Mike Smith – passwords are that little secret the you share with the service you are using that tells the server “…and this is how I will prove I am Mike Smith”.

Think about it.  If I say I am Mike Smith (and I really aren’t); without some way to prove it like a computer password, I could really cause the real Mike Smith a serious amount of trouble.  As a simple example, say Mike Smith didn’t have a password on his email (or a really simple password – which I will discuss in a bit) and I knew about that.  I could connect to Mike Smiths’ email  pretending to be him and cause all sorts of mischief for him.  As a hint, the United States Secret Service really has no sense of humor when it comes to nasty emails sent to whitehouse.gov email addresses: DO NOT TRY THIS.  That is why passwords are important – to prevent people from taking over your online identity from you.

So next, you find out that just because you have a computer password, does not mean that your account is secure.  What does this mean?  I thought having a password – ANY password – was all that was needed.  It turns out that it is quite easy for would-be criminals to either create or obtain password-cracking software.  This allows the criminal to try hundreds of thousands of password combinations until one is discovered that unlocks your account in a fairly short period of time.

This introduces the idea of “weak passwords” – something you might have heard about from time to time.  So, what exactly is a weak password?  A weak password is a computer password that would take a criminal – possibly using password cracking software – a short time to figure out.

What makes a password a so-called “weak password”.  Typically, a weak password is based on a word that you would find in a dictionary (any language).  It doesn’t need to be just the word, but the word with some numbers or even some case changes thrown in for good measure.  Examples of weak password: password, P@ssw0rd, Hello123, S3cret!, steven99!.  All of these passwords are weak – they are based on common “dictionary” words, even if some of the characters are substituted with something else (i.e. @ instead of the letter a).  The addition of numbers or symbols at the beginning or the end of the password does not fix the problem – the meat of the password is still based on a dictionary word.

A weak password can also be a short password.  Consider the math: unless you are using a system designed before the year 2000, passwords are case sensitive.  If you consider just upper case letters, lower case letters and numbers (and no blanks or space characters), a 1 character long password has exactly 62 possible combinations.  A 4 character password has exactly 14,776,336 possible combinations.  An 8 character password has exactly 218,340,105,584,896 possible combinations.  The longer a password is and the more characters you utilize, the harder it is to crack the password (the longer it will take).  Using a short password just makes it easier (quicker) for a criminal to figure out your password.

So, what does it take to make a strong password.  First of all, it should be at least 8 characters long. As you saw above, not counting symbol characters or space characters, there are over 218 trillion possible character combinations in an 8 character password; the more possible character combinations, the harder it is to break the password.

Next, consider the range of characters in your password.  There are 4 groups of characters typically available when you create your password: upper case letters, lower case letters, numbers and symbols (example: !@#$%^&^*).  A strong password will utilize at least 3 of those ranges if not all 4.  The more possible combinations for your password, the harder is it for your password to be broken.

Last, a strong password must have some element of randomness to it; it shouldn’t be based on anything you might find in a dictionary.  Remember, the password cracking programs have multiple dictionaries included with them and those words (and various permutations of those words) in those dictionaries are typically the first ones tried by the cracking programs.

Examples of good, strong passwords (please don’t use these): J87jh4k9(   %^^&*(bhjfgdln3

I can hear the protestations now.  You are saying to yourself “I can’t remember that” and you are probably 100% correct.  So, let me offer some suggestions on how to come up with a secure strong password.

Method 1: the pass phrase.  While this method may look like it violates the “no dictionary words” rule, it is none the less secure as it uses multiple words strung together.  A possible example: CanYoudothefandango?  This password is long, contains multiple words, and uses 3 different character ranges.  This pass phrase is easy to remember but hard to guess and very hard to break.  You can no doubt come up with a similar phrase that would be easy for you to remember.

Method 2 is a variation on Method 1: the abbreviated pass phrase.  This method starts off with a pass phrase as above, but shortens it up somewhat (and sometimes substitutes symbols for letters).  For example, CanYoudothefandango could shorten up to CYd0tfan.  Still secure, a little easier to type.

Method 3: use a keyboard pattern.  This insures the randomness of the password, can easily meet length requirements, can be easily remembered and extremely hard to guess.  Examples of keyboard patterns: A1s2d3f4   Zxcv1234   1!AaQqWwSs

In this interconnected age of work computers and the Internet, good strong passwords are essential.  Don’t get caught with a weak password – you may find out too late that someone else has access to your identity.